Jasper is going through this at the moment - he'd been sleeping totally fine for over a month but this week seems to fight sleep at night (doesn't like to sleep during the day, which is OK with us as that's just how it is).
It'll take anywhere from 50 mins to 4 hours to get him down for the night, we think that he's overtired and gets cranky that he's still not asleep yet. We'll rock him to sleep but he wakes up 5 minutes later crying his little eyes out Eventually he does go down and sleeps through to 7-8am, so maybe it's a growth spurt thing? Tonight we're going to try and really relax him 1-2 hours before 'bed time' with a warm bath and some massage, and watch his tired signs before we put him down.

I hear ya on the "can't do it all day" thing - especially when they're kicking and arching away like CRAZY