Also a programmer. Stepping away from the desk is often the best thing for me, not for long mind, just to smoke. Astounded by the number of times I have a programming problem and the solution just 'clicks' while I'm away from the screen. FWIW I'm not endorsing smoking, but removing yourself from the screen has benefits IMO.

I don't have too many hobbies myself, and TBH love programming and staying on the steep learning curve. Felt that way my whole working life.

The only time I've felt burnout is part of a 50/50 company where the other guy wasn't pulling his weight. When the energy you put in isn't giving you something back in the form of [whichever pursuits of happiness you have], then it's definitely time to re-consider.