I just read both 2nd and 3rd ed rules for advancement. Having never actually played any of those editions I was wondering.
Back then Abilities were either Talents, Knowledges or Skills.
Talents were intuitive, untrained abilities - things anybody should be able to do, like awareness, guile, but some people are just better at.They could only be raised by direct experience, usually on stories.
Skills are trained or self-taught abilities - things better left to professionals, like animal handling, combat, also certamen and parma magica. Could be raised by training or direct experience.
Knowledges were purely mental abilities, bookish subjects. Most types could only be raised through study (meaning: reading books). But Casual Knowledges (church lore, faeire lore, area lore, language) could also be raised by direct exposure, 1 exp per month (edit: both 2nd and 3rd ed).
2nd ed seems to not have any specific rules for training or time use (edit: except for knowledges, in the lab chapter)
3rd ed has rules for annual time use, you got 1-3 exp per year depending on how intense you train, and I assume the existence or lack of a teacher or trained could affect this. Now, this number is furthermore reduced by 1 for each story after the first you participate in during the year. Or for each season a magus spends in lab or library. Mind you, you get story exp, study from books or make things in the lab as a trade off for the lost annual experience. How teachers work to grant experience is somewhat vague.
Lab chapter outlines arcane studies from books, for the study of arts in full levels only.
Edit: 2nd ed does not have this annual time use thing. However it is clearer about studying (reading) knowledges. Labv chapter defines you get 3 exp per season of study,until your own ability level reaches the rating of the book. Also: "...but direct experience can serve, pending the SGs approval". Whatever that means...maybe you can be tauight by a teacher, with no use of books? Maybe you just practice?
So in conlusion, 3rd ed had rules for time use both monthly (for casual knowledges), seasonal (for lab and arcane library), and annual. With rules all over the place.
Edit: I find myself with nostalgic feelings about the simplicity of the experience system, with the pyramid scale without multipliers. But I don't miss the divison into Talents, Skills, and Knowledges nor the further subdivisions (Arcane, Casual etc.). Division by theme, for learning restrictions I'm ok with. And I favour a broad and short ability list.
I think Arts and Abilities should be treated separately, so you don't need to use different scales and I liked it when Arts increased full level, but I see problems with Exposure and say bonus from experimentation or Twilight. And I liked it when a library did not track every single book but rather a rating for each subject.