I have found that much depends on when I do my practice. My normal routine is to start at about 6 a.m. and to go on for two hours, often three. I would not be able to do the same in the late afternoon.
I practice both on the baritone and the tenor and allocate roughly equal time to them. Minimising physical effort is one of my aims. For example, getting a harness for the baritone made a big difference. No more shoulder strain. I also prefer soft reeds.
When I first began to practice (on an alto at that time), I felt thirty minutes at a time was quite enough. I don't think I ever felt exhausted after ten minutes. What I discovered, however, that if used what for me was a hard reed I had to put much more effort into playing.
Another thing: practicing pieces that are too difficult seems to increase greatly the required physical effort without compensating benefits.
Walter