Originally Posted by BluesDawg

Sorry, but I simply reject the whole idea of formulas and equivalences and such related to ride distance, whether in reference to age rides or comparing different activities like road riding vs. mountain biking or flat vs. hills or riding vs. running or actual riding vs. trainer riding.

Just keep it simple. Ride your age. If it gets to be too far to ride, for example, 75 miles in a day, switch to 75 kilometers (46.5 miles) or 75 yards or 75 feet or 75 minutes. Just do 75 of something to celebrate your 75th birthday.