Originally Posted by
roadie77
I think that an answer to this question framed in miles is probably not going to be the best way to go. Kilojoules of energy per kilograms of weight per week would probably be the most detailed way but it would be hard to come up with an actionable plan based on this metric. Hours per week is a pretty good compromise. My gut feeling is most people would get increasing returns on 20 minute power from moderate zone 2 sessions on 5-7 hours a week of training. Diminishing returns from 7-16 hrs per week. Almost nonexistent returns over 16 hrs.
The real limit is how much training volume you can actually tolerate, even if you have the spare time. Most average people start to struggle with more than about 12-14 hours per week of mixed intensity riding, but it varies a lot individually. It's very easy to over-train and then hit a plateau or even start losing fitness. Structured plans at the way to manage both volume and intensity and are usually goal oriented.