Esther, I started road biking at 47. I started out at a higher mileage than you, 37 miles (and it killed me) but about a year and a half later was able to ride a still-mind-boggling-to-me 375 miles. Actually, when I was able to ride 124 miles (200k) 375 was still mind boggling. (And I am not some skinny little person, either- FAR from it!)

But- fitness/mileage seems to increase exponentially. The higher your mileage gets, the bigger steps you can take! It used to kill me to add on even five more miles in distance, and if a Century was even two miles further than 100 miles, I'd feel like I couldn't do it.

So yes, just add a mile to your loop once a week- make sure you read up about nutrition/electrolytes/hydration so you are prepared when you start going longer than an hour- and you'll get there!

13-14 on flats is the speed I ride a lot of the time. When I do a very long ride, that is my average. it's not too slow!!

Nanci