Smoked for about 25 years, been stopped for 12. Sorry to bear bad news, but never noticed any reduction in lung capacity while I was smoking, and never noticed any gain since I stopped. Still glad to be an ex-smoker, though.

As for getting back to riding > 30 miles, that took very little time. I got back on the bike after a gap of close to 15 years and was commuting c.16 miles (round trip 32 miles per day) within a couple of weeks. Initially I was only able to do that three days per week, but moved up the five pretty soon. Building distance is easy, it's trying to go faster that is hard.