It's about an hour or two or a day.

This includes data from 1995 on. The early data is backfill of radio shows that transitioned to podcasts and dumped old episodes in their feed at some point. My reader itself started in 2012, I downloaded around 7000 hours of new podcasts, which works out to 1.7 hours per day. So, around 2 hours per day, since I don't listen every day, and to be fair, I haven't listened to every podcast I've downloaded, some don't interest me. But 1-2 hours of listening a day is the sweet spot for me.

My math says 365 days x 10 hours/day = 3650 hours. 8000 hours is just over 2 years, not 20.

You need to resize your napkins.