He used to wander around at night playing with all sorts of things. If we heard particularly loud/destructive sounds like thumps and bangs coming from there, we'd stick our head in and hustle him back to bed but otherwise left him to his own devices.

At first, he would end up asleep on the floor (during the warmer weather thankfully). Then he started to put himself back to bed when he was done. Now, he tends to stay in bed. We got there eventually.

ETA: Oh yeah, I should add that he used to escape, so we put a safety gate on, and then he used to open the door and throw things out, sing to us, etc (their bedroom door looks directly onto our one living area), so dh has rigged up a system where he can only open the door a crack, not as fun, so he doesn't do it really. He was furious the first few nights, but got over it soon enough.