RE: Servo lifetime
There is a life expectancy on servos, however it is not defined as there are far too many variables. Generally the first things to go in a servo are the pot and the gears. Generally though, you can get hundreds of flights on a servo. I have a plane that I would estimate that has 500-600 flights without any servo work done since installation, and I've had other planes with more flights than that.
Through high use of servos you will see worn pots and servo gears. Through long periods of time, you will see corrosion issues developing.
To be sure your servos are still in good working order, feel free to send them in for a check up.