One of the obvious consequence will be more powerful magi - up to a point (see my second remark): more time means more knowledge, more power. What a magus would have set aside because of time constraints, with 3 times more time available, he won't mind exploring/testing/spending time on some side activities. Overall, it means higher Arts, higher quality books, thus even more powerful magi.
It will be less obvious for difficult abilities and skills because of the high amount of XP needed to level, yet, it is reasonable to expect to find some expert with truly astounding level of expertise - they have time to study every tractati. By the same token, magi can reasonably look at completing Hermetic Breathrough well within a lifetime - I believe it might the single most world changing phenomena. Since Hermetic magic is more or less the only one able to integrate other traditions relatively easily, it could lead to a major power boost of the Order vs the other traditions.
My second remark refers to a post which was discussing which of Twilight or Decrepitude would get a magus first. And the conclusion was that for a reasonable magus, Twilight would become an issue before Decrepitude if we assume the 2 points of Twilight per year option (reasonable considering that after 35, he will get one point just for the longevity potion). Considering that a magus with more time might experiment a little bit more - if only because he is going faster through his pile of tractatus - Twilight can only happen faster.
So such "acceleration" would lead to more powerful magus at younger age, but not necessarily to a lot of much older magi.
As a side note, you should also consider that mundane will be more skilled as well - but again because, of the slow progression of these skills, I would expect that experts will have 2-3 more levels that currently, hardly more, more likely, they will have a broader set of skills at medium/high level.
Depending how you want to spin it, it could lead to an accelerated scientific evolution: 2-3 more level of medicine/artes liberales/philosophae make many periapts and other "natural magic" more common (three times more production), higher level easier to achieve, which will slowly benefit everybody (the powerful ones first, but sooner or later, everybody). An few extra levels in any technical/scientific skills would means more innovation, faster invention.
If you consider faster scientific progress, you might consider that people like Galileo are born a few centuries earlier - and it might challenge religious authorities earlier, possibly weakening the Church power. Could it lead to a raise of infernal influence ?
By the way, this will mean that edge traditions relying on skills will also be a bit more powerful: these 2-3 extra levels will allow them to reach higher target roll. I don't have an overall view of every ability, but some won't be impacted much (flight, shapeshift for example), other will be more interesting (weather control, entrancement), possibly much more powerful ? (Muspelli).