well, I stopped at my LHS, who is also a jet jock like us, and went over a few things. Now, these servos have been in the L-39 for almost 2 years. never a problem.
1) battery voltage. I use Electro Dynamics Battery backer system, even with the 2 - 6.0 volt batteries my voltage to the receiver is constant at 5.50, there abouts.....
2) I used an inline meter to check the servo and the draw on power, making sure I was not binding.

when I started my L-39 and moved it up to park it next to a full scale L-39, everything was fine. and hour or so later, they asked me to move mine so they can start theirs and do some low fly by's at this event IU was at.
when I started it, I noticed the right flap was not moving, but left one was ok. I then brought the L-39 back by our trucks. I left it on maybe 20 minutes, forgot it was on while I watched this L-39 fly.
late last night, I looked it over and seems only damage is to the servos and nothing else.
I was promised a ride as soon as I get my L-39 painted just theirs........ ok, I am off to by paint.....PPG?

Mark