The lives of components is based on guesses as to the use (called usage spectrums) that are used to factor the loads and number of cycles at the loads. The FAA/JAA must approve the spectrum that any given type aircraft has, but it is always a melange of the many missions that one can perform.
Even those aircraft that are continuously turning don't see all that much extra load, because they are not continuously turning.
Thos that do many power cycles are the ones to watch - 5 minute takeoff followed by approach and then another takeoff.
In any case, the spectrum is the thing, and it is an educated guess. This has been discussed in 10 or so threads in the past, and yes, HUMS could be used to help know how many cycles were experienced, but it is not allowed to be used for that, yet.