From past issues, here is what I recall on the question of "What does the future hold for this engine?"
Do these things:
Observe it starting; and running during all phases of flight. (sounds, vibrations, power)
Oil analysis history
Oil filter inspection
External appearance of engine (corrosion, leaks)
Comp testing (done correctly).
Cylinder scoping (barrel, piston, head, valve head/face/seat valves in motion)
Take off valve cover, observe for stem wobble
Where able, bottom end scoping (cam lobes, lifters)
Pull cylinder, if able pull lifters - in any case look at cam & lifters
Oil consumption
How fast oil gets watery or dark
Spark plug appearance (oil stained? burned, cracked insulation? etc)
Exhaust stack inner surface appearance
Logs - work done and age of components
Stored in high corrosion area or not (Miami or Phoenix?)
(Add yours here)
Once you have all this info, go straight to the Ouija Board and there will be your answer.
(mostly j/k on the this last point - however must say that - b/c on many of these engines, tests or observations will not tell you what is going to happen in 6-12 months Ie you will see people correctly quote "It's a crap shoot!")