I found that my best 5-6hrs a day are enough to do the work that I could do in 8hrs. With less time I'm also forced to prioritise, prune more heavily, and be creative, but at the same time, there's stuff that in the short term is always a bad idea to automate and some dumb grunt work can get it done, in which working for longer gets more done if you only care about the short term (like management loves to do).