I stay awake as long as possible. Even when I want to go to sleep, I just don't feel like I need it. I know that I'm going to wake up late whether I get to sleep early or not. I love my sleep and I'll rarely get up earlier than I have to.
I can't get to sleep unless I am actually too tired to stay up any more. I know what you mean with trying to catch up on free time too... if you go to sleep, that's the end of the day whereas if you stay up, the day lasts longer. I always feel like I've wasted the day if I haven't done anything for myself (usually just sitting at my pc catching up on the internet and/or playing games), so I stay up until I've had my fill of the day.
It doesn't help that I'm usually at work towards the end of the day rather than doing a 9-5. I'm usually doing 12-9 or 5-11 and the shift is hard to negotiate with a regular sleeping pattern.