K jet DX Mileage

Out of curiosity what mileage for a DX engine would you consider is worth adding the extra effort to keep it in good shape? Obviously good general maintenance is a given but I mean in terms of going the extra as it is worth the effort.

I ask as I have a VW campervan in which I think went in with low mileage and I do not think has covered that many miles since back in 1997 when it was installed with only 20000 miles it. I will workout the engine mileage when I am with the van this July as I can now workout from the MOTs what its real mileage is. (Clocks are not from the engines car but have now contacted the guy who did the conversion and he told me it went in with only 20000 and so can now get a rough estimate.

I guess what I am considering is it worth extra care (valve clearance checks / shims, crank gasket seals etc) if its Under 60000, 100000, 150000?

Cheers

I did not alot inside my DX engine, the head has never been off in the 270,000 miles it covered.
I got the car when it was 6 years old and 60,000 miles on the clock.
Things I did,
100,000 miles new injectors
120.000 new tappets as they are hydraulic so no adjustment needed but they did get noisy, on the new engine I have just replaced it with I did dismantle the tappets and cleaned them out as the engine had been stood outside for 4 years.
150,000 miles new oil pump as oil buzzer kept coming on.
A part from a intermediate shaft and cam shaft seal that's about all I did.
I did change my oil and filter every 10,000 miles and it had a regular service, tried to keep the revs below 3000 rpm and not thrash it till oil temp was at least 80 degrees.
Towards the end the engine was burning oil as after 27 years I guess the valve stem seals have gone hard as I could get a good blow of oil from the exhaust, the engine was still doing my 50 miles commute to work every day I just had to keep an eye on the oil levels.
I even still had the original clutch and gearbox fitted to the engine!


Edit… just read your other post about shims, If they are noisy it's worth checking the gaps, it's a straight forward job on a car but not sure on a camper van with the engine on that angle?