I had a “refresh” done on my VHPD at 26K miles (& approx 25 trackdays) - more as a precaution than anything else. I was also fortunate to know, & have the work done by Gav Kershaw & his team. The only parts REQUIRING replacement were piston rings & clutch assembly (I took the opportunity to have other stuff done whilst the engine was stripped down ie motorsport big end shells/steel oil pump shaft/ track spec clutch). However, from day one, the oil/filter had been changed at least every 3K mile, & it was never revved aboved 3.5rpm before the water/oil were nice & warm (ie 10 miles or so of gentle running. After the refresh, with an Emerald ECU, but standard cams/throttle bodies, it made 196bhp on Emerald’s rolling road.
There are people like Pesky that can do a rebuild as a preventive maintenance, but not everyone is like that.
I did mine because I had a head gasket failure and chose a (very recommended) backstreet mechanic. After the job (that’s supposed to be simple) there were some weird noises coming from the engine and after taking the car twice there and realising the guy had no clue decided to do something else.
It was then that Simon Erland made some posts about the reliability of the K and how most mechanics were building problems into the engine.
So, sent him mine and he did a complete rebuild. It turned out to be the oil galleys in the cam carrier were completely blocked with goo and consequently the cams were running dry
Time to change the cams then and while he was there he ported the head, put new fresh rings, new liners and some other bits.
He spotted the oil pump was severely worn so changed the pump gear and generally assembled very carefully the engine.
He did a superb job BTW
Most just rag the engine until it breaks and therefore rebuild the engine only after something major happens.
Some just to get more power (as Mike Lane in his K days).
And regarding the problems that lead to a rebuild, well, apart from the poor tolerances many VHPD’s are built to, there are some inherent problems, like the position of the thermostat.
Suggest you read the King K article (do a search here) and then make up your mind.