ORIGINAL: rcpattern
Scott,
I agree with you. I have found that over 4-5 flights in a session soon become counter productive. When I ran a UAV school in TX this became obvious for students. They would continually improve on the first 4 10 minute flights of the day, but on flights after that you would see some mistakes creeping in. What we would do, is 4 flights in the morning, and 4 in the afternoon. The brain simply needed a break. I have found it is very easy to get more than 4-5 flights in while practicing with electric, but I've noticed that anything about 5 I will make some stupid mistakes and I can tell I'm getting tired. If you take good breaks between flights, this doesn't apply as much. I think the brain needs time to digest what it just saw.
Just from my personal experience, but everyone is different. Even if I'm practicing alone some evenings, I will stop and walk around the field for a few minutes and such.
Arch
I wish I could recall the source... but I seem to recall (from like 20 years ago) the russians figured out that most people can really concentrate for about 8 to 10 minutes at a time with a daily total of 30 to 45 minutes....
and I think they even played around with introducing a sleep period between practice sessions... to get the daily totals higher....