yes KW i was wondering that as well,as you know on here everyone has different opinions on what/not too do...
I also cycle mine at 4.5V cut off.I knew that doing these test Static would kinda give me a idea,and with wing-load/air moving over the control surface's that it would draw more juice from the battery.
Im planning on doing it at the field as well too see what the voltage drop well be as well,and compare it.I know from reading pretty much every page on this forum ,theirs alot of questions on how much battery life can someone expect out of there battery.
I think this is a good starting point for beginners on the (How too) concept of it. with simple math.

You said "At 1.2 volts per cell nominal voltage at 6 volts you have a lot of power left.
When you go below that voltage it is time to think about stopping."
So why not Stop at 6V then and recharge? instead of thinking about it. But you are right,say i 10 flights (flying) instead of (13) static out of the 1.5Volts in my test.It well Prob be time too call it a day.

Cheers
Mike