Took the week off of work, and rode every day but Monday. By Thursday, I kind of felt drained. Then last night, I did the Tour de Zwift final stage, doing the C ride. This was a mostly flat ride on the Champs Elysees, 3 laps. Tried to hang with the wrong group again on the LONG lead-in and got shelled in the first lap. I did find a smaller group to hang with, but the problem with a small group is that riders will catch up and go past, and one or more of the group try to hook onto them, which makes the group smaller and forces you to decide whether to go with them and try to hang on, or stick with the small group. The other problem is that you REALLY need to pay attention. If you're on the back of the group and the person in front of you falls off the group, you have to respond instantly to stay with the group because if you miss it, you have to work like hell to get back on.

I was concerned that I'd feel worse than Thursday, but I felt pretty good. MAYBE I could have held on a bit longer if I had taken Thursday off, but I'm not sure. I do think, now that TdZ is over, I'll do a lighter week and then maybe do some more structure.

Regarding the 'riding fasted' thing, I have done the experiment, and I can ride 90 minutes on black coffee alone, with nothing but water to drink. But if I push it farther, I can feel blood sugar dropping, heading for a bonk.

EDIT: The conclusion applies only to me, an N of 1, so I don't claim it as a more broadly applicable result.