I thought I was the same way for a long time, but for me the kicker was 'left to my own devices' - I NEVER had anywhere near 8 hours consistently, so on the weekends, I would crash for more than 10 hours at least. My conclusion was that I needed more than 9 hours a day.

Then I went on a year long vacation - and after the first couple months of sleeping over 10 hours naturally - my body finally caught up with its sleep debt, and I was sleeping about 8 hours a day. I was amazed. Turns out I was just sleep deprived. Of course, I do know people who consistently get 9.5 hours day, so your mileage may vary. Just something to think about in this sleep deprived world.