63yo fixed-gear rider here. Started at age 55 when
I'd read that people were converting old ten-speeds and thought it sounded like a fun way to re-purpose my bicycle from 1970. Never looked back. It's my regular ride because I love the simplicity and the
direct rider-bicycle-road connection.
This past summer I toured on that bike (39x18) and had a great time. The only downside is downhill! Grinding uphill or even pushing was not an issue for me. But I missed the downhill payback