Oil analysis is a good indicator too as long as its not fresh oil. Maintenance records are good. Pull the injectors and they will tell a tale to the experienced eye. General cleanliness is a nice indicator too. High hours alone is no reason to reject.
Low hours are no reason to accept.
Do the assessment or pay to have it done. I was looking for a really good price on a boat, so I purchased one that cosmetically was not great and needed a lot of minor repairs. I am happy with that decision. A lot of the boats I was looking at, although in good repair had mostly all original everything, sails, electronics etc. The mechanic was on the boat for about 2 hours and checked everything out, I learned a lot while he was there.