Before the bonus, nobody knows when it arrives
Deciding how long to play is your call, but the bonus round is out of your hands. Sweet Bonanza gives no set schedule for free spins, so nobody can say how often they arrive in a given session. Each spin is random, and the result of one session stays random whatever the RTP version is.
Checking the RTP before you bet takes a minute and saves guessing. The RTP in play is shown only in the game rules, not in the game name. Read the rules of the version you open, because the names alone do not show which RTP applies.
Picking a bet size sets the money at stake on every spin, and the top prize grows with it. The maximum win of Sweet Bonanza is 21,100 times the bet, a ceiling reached very rarely. Treat it as the outer limit of the game, not as a goal you can plan a session around.