When I joined here, the general consensus was that without a specific "training program", you could expect to improve every year for five years or so, just so long as you cycle regularly.

With a training program, improvements come on a bit faster (it still takes time--years) and you can extend the year-on-year improvements for as long as your genes allow.

I'm in my 50s. This was my eighth season, and my best ever by every measure--speed, distance, endurance, climbing, enjoyment. While I don't have a specific training program (I don't handle rigidity well) I do routinely make efforts outside my comfort zone.

For example, while I don't care for doing timed intervals, I enjoy doing "sprint intervals"--stoplight-to-stoplight max effort dashes on my commute. (There are 47 stop signs or stoplights on my minimum 9-mile R/T commute, an average of one every 1,000 feet.) I call it racing the cars. Sometimes I even win.

I also don't care for hill repeats, but I will detour to take in a series of hills on my commute. As for distance, I won't join the club on a century ride, but I will ride 15-20 miles to the start of a half-century ride, then ride home.

I balance these with near-zero effort "pleasure cruises", what others might call recovery rides.