Last time I checked, it decreases your base harvesting time for 10 minutes. That is an annoyingly short duration. If I'm into the harvesting mood I might harvest for an hour or even a bit longer. So when I finally do remember to activate the buff I'll keep harvesting and then eventually I'll notice that its gone and have to activate it again. And again. And again. /sigh I'd really like it to just become a passive effect, not even a buff. That makes so much more sense than being a buff its ridiculous. If that isn't acceptable, then obviously making it an "until canceled" buff isn't good either. At the bare minimum lengthen the duration to be an hour. That way I'll have less interruptions when I'm into my "harvesting groove".
It's until cancelled, has been for a little bit now. Resets when you die, so you have to recast it, but it's much better than it was. (EDIT: Found a post I made when I first noticed it. Not sure exactly when it went in for sure, but it's been "until cancelled" at least since 21 December 2016. )
