Has anyone here played a magus who spent very little time in lab work, in favor of consistent adventuring or even more mundane work? Please share your experiences!
I particularly want to see if such a magus is not only viable, but able to approach a dedicated lab-focused magus in power (since the lab is the heart of most magi's advancement).
It's extremely dependent on saga type, for hopefully obvious reasons. You can only try to match the effects of years of poring over books and working in the lab if you have enough screen time to amass adventure XP and proactively find teachers and such. The value of a season in the lab is pretty consistent among saga depth levels, but spending time in the field is highly dependent on being able to put a lot of narrative focus on that time.
I'd also like to make the tongue-in-cheek remark that Redcaps are magi as well, and notoriously few are lab rats.
But really, the best way to do this is to combine your penchant for travel and discovery with a merchant's approach. If you don't want to spend seasons studying the ancient artifact, don't sweat it - sell it to someone who cares in exchange for a magic item of more use to you. If you don't want to spend seasons inventing spells, don't sweat it - trade lab texts for lessons. Don't want to be in a lab binding a Familiar for the great effects? No problem - that Magic rabbit is likely worth something to any number of magi, and you can trade it for any number of broadly useful effects, maybe even attached to otherwise more useful animals.
Independent Study (minor virtue from HoH:MC, the Merinita chapter) is your friend - +3 adventure xp, +2 to practice - designed for mystery cultists who need to quest and to practice abilities such as heartbeast, enigmatic wisdom, faerie magic, nature lore, Organisation Lore:Mystery House for which books and teachers may or may not be available. It's really good for people who don't want to be in the lab.
It really comes down to adventure frequency in your saga, and how you have Troupe play working - if you allow people to play magi a lot, the concept works - if your Storyguide insists on people sharing the spotlight and allowing the minimum of magi on an adventure and having most people play companions or grogs, your magus will be off-screen a lot, and you may as well spend a lot of time in the lab. Certainly the "out-of-the-lab" type does have the advantage they don't worry if the action moves across Mythic Europe and they need to spend a lot of time away from their home covenant.
I know a few who like to combine the adventuring and lab types - and work on transport magic. In the longest Ars saga I played, we commissioned a flying ship to explore the City of Brass, and bought a copy of the lab text from the Verditius who made it. Our in-house enchanter proceeded to build a flying castle while my original character's filia copied the lab text to build another flying ship and built a lab in the hold. You can learn magic theory until you can get the Refinement of your lab to ridiculous, and fit a full lab into the back of a wagon. You could have your companions locate Arcane Connections to lots of places you'd like to visit, and have apprentices fix the ones you'd like repeat visits to, and leap of homecoming about.
I played a Tytalus who had an enemy covenant. We started him as an advanced magus about gauntlet +30. This was about +20 more than the rest of the troupe. He had his advancement built in from the beginning. He did relatively little lab work and spent most of his time off screen on "recon missions" or visiting other covenants for political reasons (still off screen). This was done mostly because I could only show up to the game every other week or so because of life reasons, and it fit his back story reasons and that it made no sense for this character to include a troupe of other people for his revenge story--the covenant was a safe base and he helped out with building it. He was always going off on little 3-4 week personal missions. He would show up for council meetings and such but having a whole season to do labwork almost never worked out so we wrote it off to "recon". This was fun to play, but still somewhat frustrating as I had to have pre-planned a lot of his time based on an enemy I (the player) had no idea about. In retrospect, including a character written to be on a solo revenge arc wasn't very troupe friendly, even though the rest of the troupe thought it was funny as they never knew what that character was up to and often had to make up stories to cover for him.
We have a player who favours this approach in my troupe (both my current troupes actually).
I can confirm darkwing's recommendation:
and then recommend Farie-Raised Magic from the same book (indeed the same page).
This virtue allows you to learn new spells from obervation, at the cost of XPs.
Alternatively, you might think about focusing on Spontaneous Magic, but that still requires a lot of XPs spent on Arts, so probably book-study.
No labwork though.
Study bonus and Study requirement would justify such wandering behaviour. I would not remove the need to spend time studying, but for the few time he would dedicate to study, he would be more efficient than his peer.
And unless you want a highly specialised magus, once you reach a casting total of 25, he might feel he does not need to spend more time on that. And as long as he does not focus on combat spell, requiring high Penetration score, he is set.
A Rego-crafting magus does need a good Finesse and no Penetration. Lots of minor crafting can be spont'ed (Touch, Inst, Ind) or are relatively low level, increasing the likelyhood to learn more than one spell during one season if you have the labtext (or a teacher).