Well, there's the natural barrier of "sleep" by max. help being 4h. I doubt that anyone would get up in the middle of sleep just to water the tree and take advantage of those 4h. But maybe I'm wrong :-D

I don't think people would buy energy, as there's not benefit to helping besides the batch. Except for multi-accounters maybe. Instead of buying, maybe the community part could be more in focus. Getting energy or other in game benefits for a certain type of engagement.