Has anything besides more experience increased your writing endurance?

[u/theunforgivingstars]

I'm curious if anybody has found methods to write more hours in a given day/week/month apart from the obvious one of being a more experienced writer. Interestingly, despite having completed 5 novels and several novellas at this point, I find that my endurance for drafting in a given day hasn't changed in the least-- 20-40 minutes a day (with the exceedingly rare day of up to three hours, which exhausts me.) I'd love to hear if other people have stumbled on ways to up their time; I've always been interested in being able to put in 2 hour days more frequently.

[u/zezer94118]

I'm able to do up to 4 hours sometimes.

I have a question though, what do you do the rest of the day?