My original intent was to exclude those activities that, although taking a negligible amount of time per se, could only work 1/season. The goal was to only include those that could generate, or more typically substitute for, vis "on demand" for Rituals and similar magics (e.g. non-hermetic); hence the clarification that an extra hour or two would not be a problem.
The one good match for my original question was then Root-cutter, reported by temprobe. (Personal) vis sources, Philosophic Alchemy, Nature Lore, Verditius Magic and Wilding would not count. Hermetic Viresculture would not count either, in that it's basically about nurturing "standard" vis sources.
"Vis-hunting" as per Hircania rules is borderline, because if I remember correctly modifiers quickly pile up against you if you loot the same area too often, so in some sense it works as a very open-ended, contested vis source.
But I'd rather see a few extra methods that I do not consider applicable than lose even just a "good" (or borderline) one because whoever thought of it doubted whether it correctly matched the original question!