Steve:
I LOVED running. I expected to run into my grave - at an OLD age. But the best thing to do is accept reality. I could run but I don't. I don't want to wear it out. One of my running buddies, a 2:22 marathoner, had a knee replaced 3-4 years ago (he's 61 now). Now he goes crazy on a rowing machine. Goes for age group records that he finds on line. I worry he will wear out the knee but he needs to go really hard at something.
My hip replacement works very well. The surgeon seems to have done an excellent job. He even succeeded in getting the two legs the same length. (No sure thing.) How he managed that amidst the blood and obscurity of going in through a relatively small incision - but still 8" - I don't know.
Prior to the surgery I had stopped training 8 years before - trying to avoid, or postpone, the surgery. I REALLY didn't want to do it. My understanding is that the new hips fail, and need to be replaced, as the result of the constant wear and tear in the new joint which wears off microscopic particles which ultimately cause problems. I'm vague now but I researched it pretty well at the time - Feb. 2005. Estimates vary but "they" usually say hips should last at least 10 years - and often a good deal longer. Jack Nicklaus got a ceramic hip; I got X-linked poly (a hardened version of the traditional poly). My orthopedist says ceramic hips should last the longest BUT if they break it's like having shattered glass in the joint. So he prefers not to do them. I went with what he felt best about.
Now I use a Schwinn Airdyne exercise bike but only use the arms (push-pull) to avoid thousands of wearing motions in the hip. Still get the heart rate over 120 and go 30-50 minutes 3-4 times a week. I also ride a one-speed Scwhinn around town (Gainesville FL) and walk 2-3 miles 2-3 times a week. Plus pull-ups, push-ups, crunches, toe raises (500/day) knee bends (50/day) - and yard work (mowing, weeding etc.)
I was far from your level as a runner but aged well. Proud of top 5 finishes in several Nat'l Masters races at 40/45/50/55 and of going undefeated for three years after turning 40 in Florida masters races - and won all the big ones at least once (Gasparilla, Gate River Run, Tangerine Bowl Half Marathon etc) Besides the 2:32 at 44 in NY, I managed a 33:25 at age 45 in the Race of the Americas in Miami when Salazar set a then U.S. (and world?) road record of 28:02 (I think). Passed Francie Larrieu in the last mile (loved beating the good women - when I could). Since there was virtually no money in the sport back then, even for guys like you, I suspect we did it for the same reason - what my 2:22 friend told a Miami Herald reporter after winning the 1st Orange Bowl marathon in '77; "It satisfies me."