In the following thread YR7 calculated in detail longevity rituals made by specialists can reach lab total of 200.
https://forum.atlas-games.com/t/card-board-games-archive-links/116/1
This very effective ritual and low risk lifestyle (no magical research, no vis learning, no adventure, no experiments) could expand such magi's life to centuries.
Andrew's Ultimate Aging and Twilight Simulation shows 11% of the magi can live more than 200 years, and the oldest ones are over 300.
durenmar.de/aging/
These calculations didn't even counted the different immortality methods from mysteries.
I think it doesn't suit to the official line when only a few can live more than 200 years and the most dies around the age of 140-150. I like better if the magi die as the game concept suggests and not later as the current rules do.
House rule:
The magi will automatically go into final twilight when they reach warping score of 9 (225 warping points). Base time in twilight at warping score of 8 is a stress die years instead of 7 years for the more uncertainty. This way the oldest members can reach sometimes even the age of 200.
A more permissive solution would be if the final twilight comes as reaching warping score of 10 (275 warping points). But this version would let live magi too long reaching the lucky and cowardly age 250.
Twilight seems to be a suitable end for the magi than decrepitude.
In both cases strong faerie blooded magi have the best chances to live further because they need longevity rituals later.