And, yes, I'd quarantine for a good 4 or 6 weeks. The snails may be carriers for fish disease, and you'd want that to die off if you can let it. For example, if the snail has tomont on it somewhere, eventually that tomont will quit dividing and burst open to release swimmers. Now, those swimmers have to find fish to live off of, or else they will die. And that is where quarantining helps because the swimmers cannot live off of snails, it has to be fish. So, if you let the snails be in a quarantine tank, any obligate fish parasite will not be able to find a fish to live off of, and thus won't be introduced to the show tank.
Anything that has been in water and not dried out needs to be quarantined for a period of a few weeks just because there is at least a small chance that it could be carrying fish parasites.