It's high considering that you get infected every 10 plants treated after the intial grace period of 15. On average, could be just after one plant, like the appearance of bugs.

On the technical side: Seems like you can build a greenhouse room indoors, and the plant will still get light. And there is no easy way of checking if a room has exposure to the outside because of no roof for temperature purposes, other than walking every object in said room, and checking if it is covered by a roof. Plants don't appear to care about temperature and the quality is only reduced by snow accumulation. Seems like the teams that made temperature and snow didn't talk to each other. Because in the spring snow melts to puddles when the temprature is -60.

I agree it doesn't make all that much sense, it would be better if it were a cumulative effect (and maybe the count could lower/reset after some time if they wanted it to happen only after too much spraying), but that's not the point... what that poster is saying is unclear. On the one hand, it sounds like they're saying that becoming a Plantsim is hard because of the reset, but otoh it also sounds like they're complaining about becoming a Plantsim being too easy for people who don't want Plantsims in their game.

Cyjon has a fix here that makes spray numbers cumulative. http://cyjon.net/node/68

And here he has a mod that heals half your spray damage each day. http://cyjon.net/node/183

I don't want to reduce the spray damage as I love Plantsims and in fact, when I don't want to bother having them spray stuff, I'll use hacks to turn them. But I'm glad you brought these up, maybe they'll be useful to people looking for something like this!