How long do babies stay in bassinets until they need a crib?!

My son stayed in his rocker til he was 4 months old. I still let him sleep in it occasionally and he's 7 months old now.

We only used ours for 3 months.

I hear it's best to switch them when they can roll over, to prevent them rolling out

I leave them in till they don't fit anymore

We switched to crib at 6 months.