In our game last night, a character spent a season trying to discover what an enchanted item did (which I thought showed great self-control and role-playing of the 'cautious sorceror' virtue rather than just blithely using the item in the obvious way to trigger it and taking a chance). She got a total of 30 which wasn't enough to hit the lowest (and only) level effect in the item.
Do I understand this correctly (from p.100 of the rulebook)? If your InVi lab total + stress die fails to hit the level of the lowest effect, you discover nothing and the season is effectively wasted? ie: "Please come back in several years and try again".
If I were to house-rule that so that the lab total was cumulative and the investigation could be carried on season-after-season, would that break anything? eg: 30 points were built up in this season; when the accumulated "investigation total" reaches 50 (or whatever) the item effect is revealed.
If you just don't have powerful items in your saga, there might be no problems at all. But with "accumulating investigation totals", you can't have items whose powers increase over years and decades, as magi become better with Hermetic magic. Everybody will analyze that staff of the Archmage somehow obtained at once, and then use the hi level hi penetration effects in it, which dwarf everything they will be able to do by themselves in the next decades.
There are many ways - like experimenting, changing lab routines, gaining help, improving one's lab, studying some more etc. - to boost one's lab total for that second try, especially if the covenant is interested in your success.
There are things that the players cold do to raise their lab total, they could cooperate in the lab, they could modify their lab for investigation of items.
Alternately they could find a more skilled magus and make some sort of a deal to have them investigate for them (which would be a way to kick off a different story).
Find a craftsman with Eye of Hephaestus from City & Guild p71 - that allows you to identify powers put in by craftsmen, but also tell if an enchanted item actually has powers - so a crafter can tell if it's worth investigating in the first place.
I would argue that if you want to house rule how magus investigates items it is fine. As long as you think of the ramifications. As others pointed out your players might be able to use more powerful items then they otherwise would be able to. But as a GM it is you who designs the items so I donĀ“t really thing it is a issue at all as long as you think things through. =)
Having the lab-total stack over seasons still require a fair bit of time for a "new" magus to spend. Time maybe better spent doing something else? So I really see no reason not to allow it. If they where to find, and discover the effect of, a really powerful item it is fairly easy to tweek it so it is not to OP for the players. Maybe they only are allowed to use it one time every day/week or season. Or have the item have very few charges. As most of them carry a high cost to recharge, this might give you some good agonizing decisions for the players. Should we really use a charge here. We only have X charges. We probably can fix it anyway. And so on.
Yes, you understand it. Investigating is usually too difficult to be worth the effort. In four or so multi-year sagas, we've done it a handful of times. The time and effort involved can be better used in improving Arts or magical abilities. Then again, we've never had a plot where investigating a specific magic effect was vital.
There are probably a few specialists in investigating magic effects. Perhaps one can be engaged, although it may not be particularly satisfying.
My group has a house-rule that enables Investigating Enchantments to be a partial-lab activity, letting mages study or do other activities. This takes quite a bit of sting out of using their personal time to investigate magical items the ST plants into the game. Failing to find a power becomes more of a, "Well damn, I guess we should investigate Magic Item B then!" rather than a "I volunteered to do this and got nothing out of it, and we still have two other magic items to investigate!?"