TSMOH alone doesn't tell you much. The condition is what matters. There are many examples of brand new engines failing within the first 100hrs and many more examples of decently maintained engines ticking along well past 3000hrs. 150hp mogas O-320s I flew as a CFI racked up ~3500 hrs in some cases and may or may not have had a dash of MMO here and there...who's to say? In fact, a low time engine is much more likely to fail than a high time example if the same engine (I'll search for the backup to this claim and post it here if I remember). Give me a 2000hr O-470 over a 10hr O-470 any day of the week!
TBOs for most horizontally opposed engines range from a low of 1200hrs on some of the older geared engines to a high of 2400hrs. The calander limit is generally 12yrs but nobody ever talks about that. TBO is not really a good indicator of engine life, though. In the US, we run "on condition" meaning that the TBO is merely a reference, not a limiter. If the engine is healthy and is not giving you any bad signs then there really is no reason to drop ~$30,000 or whatever on an overhaul.
Each manufacturer has a list of their hour and calendar TBOs but, again, they don't mean much to a part 91 owner/operator. Certain commercial operations must adhere to the hour and calender TBOs but even then the FAA will grant extension waivers in many cases.
Personally, I would not hesitate to buy a plane with an engine at or near TBO...after a thorough inspection, of course. I'm confident I can get another few hundred hours out of a healthy engine. And if I don't...fine. I priced the engine as a runout and will drop a mid-time engine in sourced from someone doing an engine upgrade!
Published TBOs for common piston engines:
TCM - http://www.continentalmotors.aero/uploadedFiles/Content/xImages/TBO%20Page%20SIL98-9C.pdf
Lyc - https://www.lycoming.com/sites/default/files/SI1009BD%20TBO%20Schedule.pdf