OK, my question is simply this; How long should we expect servos to last? Is there any rule of thumb about when it might be wise to change them even if they're still working?
Today I had a crash due to a servo failing. It's a JR DS811 and is on the aileron of a Raptor 50. I have had this Raptor for about a year and a half and bought it 2nd hand with these servos on it and up to now they have all worked fine and have given no hint of potential problems.
At the time of the failure I was just doing a gentle circuit when the heli suddenly began to roll on its own and I had to flip in some negative pitch to stay airborne and then hope it would roll back around upright again so I could set it down. I did manage to get it set down more or less on its skids but there was still a fair amount of damage.
Back in the pits everything was working except the aileron servo, it appears the motor in it has just decided to expire.
Are any of these servo testers able to spot a potential problem?