In most sagas I have either been in or guided myself players are new characters, almost exclusively coming into the convenant from the outside in their post-apprenticeship life.
In these same sagas, I believe two out of eight apprentices have stayed with their home covenant, while most others have moved on for various reasons (lack of resources, character's desire to move on, lack of player desier to run another character, etc.).
Now I have no idea if this is standard or not, but it does suggest a couple of notions.
First, much like universities, magi train in one location and then settle in a different one.
Second, the Order of Hermes involves a lot of traveling.
So are these notions true for your sagas? Does almost every apprentice pick up and move on? Do any of them stay?
My observation is few people like to play under the thumb of senior more powerful magi. Because of that, most campaigns start as a group of young apprentices come together and create a new covenant. This would suggest to many that this is the standard thing- apprentices leave and make a new home.
I think in a 'real world' it would be very difficult to leave home, in particular in the middle ages. The notion that a person with the gift could journey to some foreign area, meet others and set up shop seems very unlikely to me. It seems to expensive and given the social flaws the gift carries, even if one could over come the money issue, I think it would be hard for a magus to start a covenant from scratch.
My approach is a variant on the initial senario. The magi are apprentices who left their homes and started a new covenant, but they are the exception to the rule. Most magi would never dare to take on this challenge as the resources and security of an established home are to comforting. So in my game the characters are the exception to the rule, the standard being apprentices stay at home. That's my take.
I believe that most masters vue their apprentices as extentions of themselves.
If it serves them to keep them within the alliance then they will pull strings to ensure this is what happens. If they have an arrangement to setup a foothold into another alliance, they will send their apprentice there.
Sometimes, if the master is evil enough, he might even send his apprentice to try to found a new convenant that in the end will mine the ressouces of an ennemy convenant. It could also be to prepare the venue of the master in the event that a special phenomenon has been found & the Master has an interest in studying it. Send the apprentice establish a foundation & then move in a few year later.
Basically, I think over 90% of the apprentice follow the plan of their masters. Of this 90%, atleast 80% are requested to stay @ home. the remainder are sent to one of the above missions.
Now, the first 10% that do not obey their masters can get a number of interesting flaws at caracter creation
