Jim,
Over the years I've found Vref to be pretty accurate.
You rarely get what you put into an airplane out of it at sale, which is why buyers look for an airplane with all the bells and whistles already installed rather than put them in after purchase. Paying $20,000 or so to put in dual 530s and a coupled autopilot in a 150 isn't going to increase the sale value of the airplane by that much; just doesn't happen. (Although I've sure met sellers who spent some time thinking that because they had %40,000 in a 150 that they should get that out of it at sale before the realities of the market disabused them of the notion. None came close.)
Agree with you 100%, TBO is only a bit of information. But without solid engine monitor information, oil analysis results, good compression check and clean borescope results, a buyer is going to shy away from an engine that is well past TBO "just because". sigh
A friend has a 310 with both engines more than 1,000 hours past TBO, running great. He monitors the heck out of them and runs them lean of peak to keep temps down (which is one reason they lasted so long) but recognizes that the resale value of the airplane right now is with runout engines.
Best regards,
Rick
