For me it's always been "how much can I take?" That's less now that it was, even last year. I try to walk the knife edge between enough and too much. I can ride as much as I want because I'm never bored riding. I have a set of resistance rollers out in the shop, which can be heated in winter. I can do anything on them that's good for winter training. I don't ride outside more than once a week in winter because it's usually raining and I hate spending time cleaning a bike which I could instead be riding on my rollers. I don't have any trouble getting in 8-12 hours/week between riding, gym, and other cross-training, and that's plenty. I got the same hours in back when I was working full time. No kids!
I do other things which I have to do to be able to ride as much as I can, namely hiking and strength training. Just riding never worked for me. It's too limited w/r to range of motion and muscles involved. Over time stuff you don't use on the bike gets weaker and stiffer and sooner or later you get injured, and then you're off the bike and doing rehab for who knows how long. Trying to figure out how to balance that has been a focus of mine. Plus I like the feeling of "I can do anything I want." Well, I don't rock climb anymore. That's gone and it's not coming back, but then I'm done with that anyway, so no loss. I can hike, backpack, snowshoe, XC ski, Alpine ski, walk, run, gym, and that's all I really ever wanted to do. Biking is still the main event because it's so much fun, it's generally a low body stress thing, and one can't ski in the summer. I keep the non-biking activities down to a level where they add to, rather than subtract from, my ability to ride. So far, everything still works, though I'm probably looking at getting a pacemaker this winter..
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