What is good to only change piston rings or change piston rings as well as headblock and valves?

Piston rings sometimes wear if air cleaners are not serviced or removed and dust gets into cylinder- used to be common on cycle run with velocity stacks with coarse screens instead of proper air filters. Standard rings can be replaced without a bore job- just a ridge ream- once or twice. check cylinders and heads, maybe a valve adjustment? if intake valve lash has closed from lack of maintenance. Clutch plates? Shouldn't be a fuel economy problem-- slippage from abuse would be obvious.