54 here
1. Trek 7500 fx
2. as few as possible.
3. I'm much slower than when I was in high school, but quite a bit faster than the past 25 years or so...
4. Since second grade, but then I stopped at around 25 and didn't pick it up again till last year, and not seriously till 2 months ago.
5. Mostly fitness, but I'd like to do a century next year.
6. 5-6 days a week, around 100 miles a week now (up from 50 at first) - 15-20 weekdays, with a 30+ longer slower ride on Saturday. Maybe 2000 miles this year, looking at 4000+ next year unless I flake out.
I'm mostly focused on fitness and weight loss - I've done a lot of walking in recent years, but I found that just didn't keep the weight off - and running is out - the knees won't take it. Biking has been every bit as fun as it used to be and seems to be working for me - I can't believe I stopped for so long.