Before the spin, not after the bonus
Deciding how long to play starts with one fact: nobody can say in advance how often the bonus round comes. The result of one session is random, and the RTP does not change that for a single visit. Volatility is high, so long stretches without a feature can happen, and a burst of wins can arrive without warning. Set your limit before the first spin.
Picking a version starts with the game rules, because they are the only place the RTP version in use is shown. Do not judge the return from the lobby thumbnail or from anyone else's session. Check the rules before your first spin, and read the figure for the version you are playing.
Weighing a bigger bet against the top prize means remembering that the maximum win is a ceiling. It is reached very rarely, and the figure says what is possible, not what to expect. Keep your stake small enough that a dry session is still affordable.