There is a tournament limit of no greater than 300fps, some events elect to embrace a lower limit of 280 but there are no hard and fast rules as to what it should be but just as long as 300fps is the maximum.
As far as how close you wanna push the limit ?
It really depends upon several things, if you are playing a tournament then it's within your interests to push it as close to the top limit as is possible ... if you have good paint and a good marker, then you can nudge it toward 290 which is what the pros will try to do .. they generally shoot the best paint and the best gats and so they will tend to push higher.
As for scenario and walk-ons etc?
You don't need to chance yer arm and 285 is about right I think as long as the limit is 300.
It's all about safety first hence the top limit of 300, and risk of penalty second .. get the balance right and you shoot your optimum game, get it wrong, and you let your teammates down and can lose an event because of it ...
Your call ..... but it's you who will go from a hero to a zero in the blink of an eye, or in this case, the blip of a chrono ....