I'm 50 and have been riding since I was about 20. My mileage varies as my interests change but it's been a constant that I ride at least in the summer months.
1. I ride a Madone 5.2
2. No supplements but for longer rides I use Hammer Gel, Skratch Labs drink mix & Hammer Recoverite
3. I don't think I've slowed down at all. I average about 32-33kph on round trip rides & that includes stop/starting at lights though I tend to head out of town so that's minimal
4. 30 years
5. I ride Mon-Fri on a 25k loop and on weekends I go for longer rides, usually about 80k each day. This weekend I did a metric century on both Sat & Sun
6. Daily. I bought the Madone on Aug 1/11 and hope to hit 10,000km but this August. I'm at 8,450 as of today