I've had similar symptoms for 7+ years now so it's most likely for life. Have seen many infectious disease specialists and CFS/ME is the diagnosis (same as long-covid). Mine seems to have been triggered by Glandular Fever (Epstein Barr Virus).

Exertion is the biggest trigger for me, but also the prescribed cure (Gradual Exercise Therapy). Alcohol is a weird one, I often feel better with a hangover than I do on a bad fatigue day (immuno-suppressant?) but then way worse the days after. I also have recurring Mononucleosis symptoms and have tried anti-virals to no avail...

It's so obviously immuno-related, really hope the science progresses soon.

Some interesting articles: https://www.gavi.org/vaccineswork/what-happens-when-you-dont... https://edition.cnn.com/2021/03/12/health/ron-davis-covid-lo...