Apparently you need a Season of Lab work and a pawn of Vis to make an active (at the beginning of lab work) Arcane Connection into a permanent Arcane connection.
But is that single activity all you can do in the Lab for that Season?
Could you fix more than one Arcane connection (eg the shed scales from different dragons, or hair clippings from various Magi) in a Season, say up to your Vis limit?
Other lab activities?
or here, or any number of earlier threads.
It crops up alot because it feels like a waste of a season, and because it can be argued that using the mutiple lab activities rules, you could easily fix up to (MTx2) ACs in a season.
My advice:
House rule it either way in your troupe, but understand that it will be a house rule either way.
Also, note that there is no lab total, so make use of the rules for interruptions to seasons. No reason you can't adventure for a month and then fix a Arcane connection for the reason of the season. Also, remember that Ars Magica is a rules set that allows you to change the rules, in game. Use the Original Research/Ancient Magic rules. Getting a Breakthrough is not that hard. Make it legal in your game to fix MT/Arcane Connections a season!
We do month by month experience rather than by season so it was easy to house rule that an AC takes 1 month to fix, not 3. It has been done once in 6 elapsed years of the game (we run slowly and pack a lot of detail in).
Sahirs in Cradle and Crescent can do multiple things in one season in their labs, including fixing Arcane Connections, because every lab activity for them has an effect level. Hermetic magi can't do this (a flaw in Hermetic theory, presumably), but they could discover this process from their Solomonic counterparts.