I am an active rider that typically does 10 - 20 mile rides at a 14 MPH pace in rather hilly terrain. I did a 37 mile ride yesterday at about the same pace and feel fairly good today. I am 54 years old and have done century rides when I was in my 30s but none since. Is there a minimal training plan I can follow at this point to have a chance to finish a 200k ride in early October? I am thinking something like maybe 50 miles this weekend and then a 70 mile the following then the 200k on the weekend after that (and still doing 10 - 20 mile rides every other day in between the big rides)? Is that doable for an old fart like me or are my ambitions beyond reasonable hope?