Strava makes it easy to keep track: about 3,500 miles outdoors, 1,500 miles indoors on Kickr/Zwift.

Of that 1,500, maybe 100 are miles I would have ridden outdoors if I didn't have the trainer and Zwift. So, 1,400 miles or 80-90 hours of good exercise added to my yearly totals

Actually, at the local gym and when on travel using hotel gyms, I also get indoor cycling in several times a week, but don't track that. Probably another 50 hours worth.