I move mine when they reach the weight limit - I can just see that I keep one in there over the weight limit and something happens...not good.
I have them in cots and they know they are not allowed to get up until I am the one getting them up - I have lucked out and they have all listened. I do have one sleeping near the playroom however so I actually use my extra gates and gate her in so she cant move and I tell her I have a monitor on and can hear her every move