Airframe condition on a high total time airplane is something that can be assessed in a good prebuy. Book price is lower on a high time airframe so with a little luck you may get what you paid for. I have a Warrior with 8,000 on the airframe and the only "high time" maintenance I've had to do in 6-7 years of ownership is rpelace all the control cable pulleys and other associated hardware. I do not feel 5,400 ours on a 25 plus year old airplane is "high time". Engine time on the other hand is a whole different deal. Time remaining to overhaul is something that you are paying for in the book pricing of the airplane. It is also more difficult to assess the condition of an engine so there's always a possibility that you are paying for something you won't get. If you can crack the nut it's best to buy a runoput and overhaul it. Then you have control of what level of overhaul, the quality of maintenance after overhaul and how the engine is operated. The 172N has the dreaded O-320-H2AD engine that eats camshafts and tappets. That's the bad news. The good news is unlike other Lycoming engines the tappets acan be removed and inspected during a prebuy. An H2AD operated FREQUENTLY and having the oil changed at reasonable intervals may well go past TBO. Charlie Melot Zephyr Aircraft Engines