... I can't help but wonder. I realize YMMV; it's an impossible question to answer and all but here it is anyway
I was pretty much inactive for 20 years... sat on the couch and played my guitars, mostly.
Oh, my wife and I would do some hiking and walking on vacations but, let's face it, I was a slug.
So, I started riding (how long ago? you been paying attention?) and I do about 130-150 miles per month.
I do some short climbing -more now than a year ago- and, of course, I live on a 500-600 foot, 11% hill.
I am definitely developing some musculature in the legs, the quads are coming along... the calves are... well, the calves are there. They were pretty lame before. So much -ok, ALL- of riding is about strength to weight ratios. The weight is slowly coming down, the strength is coming up. I guess oxygen intake plays its part, too; how much does asthma hold me back? Will that be my limiting factor? Is it now? Oh, along those lines, I'm going to see a cardio for a stress/echo in a couple of weeks. Maybe I'll finally find out what my HR limits are. I'm really looking forward to that.
OK, how much development should I expect to see and how fast? I see where I am now, where will I be in another year? Is it a fairly linear thing or more of a punctuated equilibium? At what point do I have the strength I "need". When do I start having legs like the Incredible Hulk? Yeah, yeah, as I said above (and as I've said before) I know this is highly variable and very, very fuzzy but it might be a good jumping off point for discussion.