Thoughts on running an engine past TBO if it's flown regularly, oil analysis, oil change and check the screen every 50 hours, and check compressions every 50 hours?
What is TBO on that engine? Is the engine TBO is 2000, or is it 1600? Makes a difference as to how much further one is expecting components to last. Has any mechanic been into the power plant with a good borescope it might give you a general idea of the health and if there is corrosion.
Bottom line engines are expensive. It sounds like everything is being done to ensure reliability on a past TBO engine. One thing you have going for you is this is not a turbo charged/high power engine, however failures can occur that could do severe engine damage, thus necessitating a bigger expense down the line. There is a reason for TBO limits from the manufacturer; this limit gives you a reasonable time frame for reliability. With that being said I had an engine fail on me after 100 hours, but that was due to a bearing failure. If you have an engine overhaul shop that you trust, or other mechanics that you know well, I would run the question around the room. During an engine overhaul, there can be many serviceable parts, such as the crankshaft, crankcase, cam shaft, that all get put back in during a rebuild. Parts such as bearings, pistons, cylinders, and valves are worn out and not used again by the time the engine makes it to TBO, and at this point in your engine, are probably not as healthy as say your crankshaft. The other question is how many overhauls has that engine gone through? If major components were replaced last time (ie crankshaft), they could be good for several more overhauls. But if a part like your crankshaft is older, it could be out of limits now even though the engine is still performing well, until it does not perform at all. As in everything aviation, we try to control what we can, and deal with what we cannot as it comes up. Your question is a tough one for sure, a balance of cost vs reliability and monitoring the health of the engine through preventive measures. Bottom line, this answer comes down to having the best information you can find from experts, and then determining what you are comfortable with. Clear as mud? But I do understand the situation you face with your powerplant.