I have some reservations about the abilities limitations for starting characters: namely that if a child were to spend 1 season a year from age 6 to 8 training in their parent's profession, then apprenticed in the same profession to their parents for 6 years, this would give them 96 points in that ability by age 14 (assuming an ability of 5 for their parent), but according to the rules they can't have a skill over 5 until they are 25, even though at this point they are only 9 points away from skill 6 and age 25 is 11 years away. If they were (at the age of 14) to begin a normal career in their profession between 14 and 25 at 2 seasons of 2 experience each per year they should receive another 44 experience. The suggestion is that these points should go into leadership and guild lore, but if the are somewhere without a guild it would seem to me that 6 at least would be a better goal score to stop at, since with skill 6 and leadership 3 (30 points) and assuming an average assistant score of 4 this would allow for a worskshop score of 12+stat before enhancements due to updating or better supplies. Perhaps it would be more appropriate to limit 1 ability to 6 and all others to 5 by the age of 25?
Remember that the character has a life outside of work; and can thus always spend exposure experience on the local language, local area lore, and other abilities related to their day-to-day life (bargain is relevant for most professions)
The ability limits seem to be intended to simulate this fact, by preventing you dumping all your XP into one relevant skill.
The thing is that it wouldn't be dumping all of your available points, and given a trainer with 6 skill you could reasonably expect for the apprentice to finish with a skill of 6 as well, if that apprentice had spent 3 years of childhood training for 1 season before beginning apprenticeship where they spent 6 years putting 4+training points into their craft (or 13 points/yr) if you put all of your available points into your craft (spend the off season studying, because you are insanely focused) you get a calculated 120 points by the end of apprenticeship or 129 with a skill 6 trainer- aside from the fact that apprenticeship couldn't go on for 6 years because you would already be of equal ability to your master. To avoid that your father/master would have to be ability 7 which would leave you 2 xp shy of 7 when you finished your apprenticeship in 6 years. In fact after 3 seasons if training with the father/master prior to apprenticeship for ability 5 a person could finish apprenticeship in 3 1/4 to 4 1/4 years if they either put all experience or all exposure and training experience into their ability score.
In many cases, to be good at a craft requires more skills than just the primary skill in question. For instance, Craft: Weaponsmith 5 is good, but having a good Bargain, Folk Ken, and Leadership may also be helpful. City & Guild goes into more details on this.
As kingreaper and vimcdonald said, while it is possible to exceed the stated character limits, it requires an unlikely focus on the part of the character. An apprenticeship of 6 years means 6 seasons of training plus 12 seasons of exposure to job related skills. A balanced apprenticeship would put maybe half of that into the primary skill -- ok, your job may be making horseshoes, but shouldn't you know a little about horses, about who your clients are, about bargaining with said clients etc.? At 6+3=9xp/training season and 2xp per exposure season, that means 39xp, i.e. a score of 3(9). A very focused 6 year apprenticeship that puts 2/3 of all xp into a single skill gives you 52xp in that skill, i.e. a score of 4(2).
Note that ability caps do not apply if you take the "very detailed" character creation option whereby you walk your character through his apprenticeship season by season. But if you don't, they do provide reasonable, if slightly "stingy" guidelines of what a "normal" character would experience.
I have to agree with the above posters; it takes more than just the one skill to be good at an entire profession.
Let alone certain professions that require multiple skills, or skills which the apprentice in question wants to learn.
In London in the 1500's I believe the Swordsmiths guilds and the Cutlers (knife-makers) guilds engaged in gang warfare with swords and blades. You think these apprentices didn't have at least some knowledge of the use of their weapons?
As well as the direct proffessions, most of the hale and hearty medieval men, peasants included, would have had some skill with Brawl and Athletics. Why?
Because boys and teenagers love running around, lifting heavy things and wrestling and it was seen as an excellent use of time for peasants; fisticuffs wasn't for nobles, but the peasants sure got into it. Think these boys wouldn't have recieved some unofficial training from either their master or an older wrestler? On top of this, what of a season here or there for being in a militia in things like Great Weapon?
Plenty of skills out there to learn. Very few people without Driven or Obsession would get much past 5 before the age of 20.
I'm not suggesting putting all their points in one skill, simply pointing out that it makes sense to allow one skill (presumedly the primary professional skill) to be taken one level higher.
The problem SilverOak, is that once this is "allowed in canon", then people being people, it will become the new normal, as level 5 is now (despite the fact that 5 is probably too high for all but the most driven young men). But it's your game. Make a major virtue that allows what you want to do here. No one is going to accuse you of "powergaming" if you take a major virtue for +1 to your max skill level!
I may be wrong, but apprenticeships usually don't last six years (or actually eight years as you describe, now that I read it again). Depending on profession maybe three to five years, after that (and maybe even before) you're supposed to work on your own. So the scenario you're describing would not be standard - which is what the limitations try to emulate.
[Edit] The way I see it: As an apprentice your master maybe spends one season a year training you one-on-one (8 XP, given an ability of 5) and the other you do menial work (2 XP for exposure), netting you 10 XP per year (free seasons are exactly that - unless you're a workaholic maniac you're not gonna spend them in the smithy). Given three to five years of apprenticeship, that nets you 30 to 50 XP.
City and guild p. 43 lists lengths of apprenticeships ranging from 8 to 12 years, with 7 as the standard. It also describes the training as 1 season of training, two seasons exposure, and one season of practice (same page) for 16 xp per year in the craft, which over 7 years would be 112 xp. There is also the issue of ages- if you apprentice to your father and begin at age 7 or 8 then you already have 2-3 years of following him around while he works at home and trying to emulate daddy. Then there is the ages chart on p. 42 of city and guild which describes someone being an apprentice from age 10-20, which would be 10 years of training or 160xp. Of course this also shakes the foundational idea that masters will have a skill of 5 if that much experience is gained during apprenticeship...
... given the degree of father to son education in the middle ages maybe it should be the standard... one skill up to 6, all others 5 or below.