All british aircraft post WW II have fatigue life's
In the RN Heron I owned it had a fatigue meter fitted.
The Heron had two fatigue lives 15000 and then change the spar then an absolute 30000 hours
My aircraft had 16000 hours TT but a fatigue life of only 12000.
I soon learnt to religiously ensure the fatigue meter was working.
Also discovered if you did a sector length of 3 hours in calm weather the meter only read around 1.2 hours.