f.lux is an awesome little thing I had installed for months. Then on the excitement of moving to a new place, I removed it. And I could stay awake thru the night again. So it wasn't old age after all. Now I will put it back again.
I use f.lux and think it's great. I recently started taking a small amount (~1.5mg) of melatonin after reading a post[0] by Gwern and the accompanying discussion on HN[1]. I find that taking it ~30 minutes before I want to go to bed makes it much, much easier to "tear myself away" from the computer, book, etc. and go to bed.
Bright blue light disturbs your natural sleepishness feeling (melatonin/etc), so the need to sleep is felt as, say, exhaustion which is different and comes later.