DS is 3 next month and we still use a monitor in his room every night.
He sleeps in a double bed never falls out (anymore) and if on the rare occasion he gets up in the night he comes straight into us but I still keep a monitor on when he's in bed.
What age did you get rid of yours?
We live in a relatively average sized 5 bed detached and I guess we would probably hear him but I have kept it to now just in case we don't or if he has a nightmare and we wouldn't hear.