Congratulations. You're doing great if you're satisfied.
FWIW, I started riding at 64 and decided to JUMP IN DEEP! (That's always been my standard style (idiocy?))

• Week 1 (starting 6/1/2010) = 3 rides, 27 miles total, long ride 13 (a group ride)
• Week 2 = 5 rides, 103 total, 38 long (group ride)
• Week 3 = 4, 127, 45 (group)
• Week 4 = 6, 162, 40
• I decided I was going to stick with this, so I stopped riding my 35 year-old Lotus with a used CF bike with indexed shifting.
• Week 5 = 6 rides, 241 miles (!!!), long rides of 48, 51 (Wednesday club ride), 56 (Sunday club ride), and 60 miles
• My insanity continued to the end of the year.
• Week 15 = 2 rides, 47 miles on Wed, 1st century on Saturday (15.3 mpg avg, AHR 127, MHR 144, avg cadence 83, avg ascent per mile 49')
• Week 16 = new bike (also used, CF, better fit), shakedown ride on Friday (15 miles), 2nd century on Sunday (15.3 mpg avg, AHR 123, MHR 150, avg cadence 85, avg ascent per mile 57')
• Total to end of year (7 months total) = 4,945 miles - that included riding in weather as cold as 16 ° (I don't do that anymore)
• 2011 = 4300 miles total, 4 rides in Jan, 0 in Feb, and then I lost the final 8 weeks for prostate surgery

This was NUTS, but it might give you a sense that it's possible you have less limits than you think.