This is anecdotal, so not data, but I'm not 100% sure i agree. But it may be an age thing.
In my youth (for some definition of youth) I could work flat out for 10 hours+. I'd get in the groove and just fly.
I'm a little (or lot) older now - and I can do maybe 6 hours at a time now. I now fill the rest of the time with non-code work, like docs etc. Or I just knock off early.
If I have a solo code task, I can do a 10 hour day without feeling burned out. But a day of randomizations, collaboration and firefighting, I feel done after 6 heh.
In my youth (for some definition of youth) I could work flat out for 10 hours+. I'd get in the groove and just fly.
I'm a little (or lot) older now - and I can do maybe 6 hours at a time now. I now fill the rest of the time with non-code work, like docs etc. Or I just knock off early.