I'm not sure how to define "old", but I'm two months shy of 56 and I pretty much only ride my Trek Roscoe 8, which I bought a few months ago.
I've been very into bicycles since 2011 and part of the thrill is learning new things about geometry and fit and what I thought worked for me has changed drastically, over that time. The Roscoe has been a HUGE leap forward in that understanding.
First, the Roscoe's reach and effective-top-tube are ridiculously long. I've struggled with hand/arm/shoulder discomfort for years, until I discovered that I was going in the wrong direction (ie, shorter) for reach and that a longer reach is actually more comfortable for me. I rented a large Roscoe 8 and when I made the decision to buy one, I planned on getting a Large, even though I had some shoulder issues while riding that size. I was fortunate that two local shops had both L and XL Roscoes on the floor and totally on a whim, I test rode the XL and as far as reach goes, it just fit me like a glove. It was a literal night and day difference in comfort and the guys at two different shops mentioned that based on observation, the XL worked better for me. Once I bought the bike, I started experimenting and ended up adding 3cm of reach, via a longer stem.
Second, I've been riding bikes with "laid back" geometry (ie, slacker seat tubes). The Roscoe, accounting for fork sag, is close to 75 degrees, which is much steeper than I've been riding and it just works for me. My pedaling efficiency feels much better and because my natural riding style is to sort of hammer it, instead of leisurely cruising, the steeper seat tube angle works for me.
Because I will probably do very little singletrack riding (it was my original intention but I discovered that an eye condition that leaves me with very poor vision and depth perception immediately in front of me makes riding on very uneven terrain very difficult) and I'm undecided on chainstay length and bottom bracket height (Roscoe is short and high, while I might still prefer long and low). I definately like the higher trail and wider handlebars and am now looking at rigid bikes with similar geometry (Stooge Cycles, I'm specifically looking your direction).
I had the shop put better pedals on it before I even left the store and I've replaced the grips with some Ergon's. Future planned changes are swapping out the dropper post for a regular, much lighter seatpost, swapping over to some lighter, faster rolling tires and maybe replacing the handlebars, which feel like a solid bar of steel, with something lighter. I calculated that these changes would shave about 2.5 pounds off the weight of the bike, which isn't all that heavy to begin with, at least by my standards.
For now, the Roscoe is an amazingly versatile, very fun bike to ride. Even riding around my sub-division (which is 95% of my riding), the suspension fork really helps my torn, arthritic riddled shoulders when I pass over the pavement buckles that seem to occur about every 30 feet, in my <20 year old neighborhood.
