What counts as mid time?
Half way to TBO. 750-1000 hours I would say.
A mid time engine is a good criteria when shopping, but only if those hours were flown close to each other. If the 750-1,000 hours were spread out over 20 years, there is likely corrosion that will kill the engine long before TBO. I bought a plane with a mid-time engine, and still found metal in the oil filter. It turns out the plane and only flown a few hours in the past 2 years and the camshaft was badly corroded. Fortunately, this issue was caught during the pre-buy inspection and I re-negotiated the purchase price down to pay for the needed repairs. A new engine can cost as much as a complete used airplane, so be careful when shopping and ALWAYS get a thorough pre-buy inspection.
