Ha ha Comanche... Tetchy, overrated and a maintenance black hole. There's stuff around with a lot less than 400HP that will do better with wheels sticking out ....
Any aircraft can be a maintenance "black hole".
What "Stuff" are you talking about? I'd be keen to see a list that has the speed, payload, range and versatility of the a Comanche that can land on many shorter grass strips.
The IO720's seriously unreliable. BIG wallet is a pre requisite.
Whilst I no experience with the 400 Comanche I know of no major reliability issue with the IO720 providing like any engine they're maintained properly.
I suspect many are run at 65% power or less, probably close to 55% truth be known, the engine isn't working that hard. The engine should go to TBO without too many issues.
Sure at overhaul there's a bigger bill, but I would suspect no worse then two IO360's or some of the TSIO 540 variants.