you say you were "pooped" after 20 miles? pooped due to lack of proper nutrition during the ride - or the cancer? If you can do 20 you should be able to do 30 but you do need to be sure to eat and drink during your ride.......drink about every 15 minutes, more often if it's hot and eat about every hour. Some people say to eat every so many miles but if you're riding say 10-12 mph, eating at 20 miles could be too long to go without. More than anything - it's Your day!! It's Your ride, enjoy it! Pick places you want to go, things you want to see and take all the time You want! and let us know how it goes!
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, champagne in one hand, strawberries in the other, body thoroughly used up, totally worn out and screaming: "Yeah Baby! What a Ride!"