I think it really depends on the LO. For us, we occassionally make the decision to go for a late night and hope for the best (special occassions like my brother's wedding, and even not so special occassions like a get together with friends we just really wanted to stay at). But, in the case of my DD, we WILL pay for it. This is just how she is, she's very perceptive to stress and other's feelings, and she loves her routine. So, without doubt, I know we'll get NWs, or EWs, or her behaviour will be horrendous. That's just how she is. Other LOs are much more flexible than she is. It's just about knowing your LO, and deciding what he can handle and what, if any, the trade off may be and being prepared for that.