It is a concern to some Rob, remember the early gas turbines late / post war etc were built without any lives on them at all and were never expected to last but a few years, so you could legally be flying a 1945 meteor with its original engine in it in theory, something the manufacturers would never have envisaged.
You go back to 1945 and you would have been laughed out of the building if you had said I intend to buy one of these in 60 years time and fly it as a leisure pursuit.

As for 20 years, you do realise that although a private piston spam can has a life placed on the engine of 12 years and XYZ hours, ( plus an allowable 20% extension by the CAA) If that aircraft is privately owned then the engine can continue in service ” on Condition” after the life period laid down by the manufacturer has expired. It is one thing I always thought was wrong.

I believe when the RAF accepted the Meteor into service they quoted that both engines required less maintenance per flying hour than the Merlin in Spitfires.