J41 getting on for 15 years plus if my memory serves correctly. Saab 340 pushing 25 years old.
Don't judge the capability of an aircraft by how many were built. The most impressive turboprop I have ever had the honour of a jump seat ride in was the Saab 2000, many moons ago in Switzerland. Total built: 63 ish.
Mathers perhaps it's worth considering this. If Highland don't use their aircraft in between rotations there are a lot less potential opportunities for the core business ie the Cardiff-Anglesey to be disrupted by other routes. Someone earlier used Cardiff-Aberdeen as an example. Aberdeen is a long way from CWL if the aircraft went tech, had a slot delay, was grounded by weather and so on. As someone alluded to earlier Airlines do not have fleets of aircraft standing by in order to mount a gallant charge at the first sign of trouble. Thus some might consider it an enormous privilege to have an aircraft and necessary attendant crew and support staff at their sole disposal.
James