The recomended engine TBO is based on the most economic time to OH.
After the recomended TBO the crankshaft bearing journals start to wear oval and as the crank can move more in the bearing it also wears oval ,the chances are that if the engine is run "on condition" for a long time it will take the crank below the regrind limits and so put up the cost of OH by about 20%.
I have no doubt that some contributors to this forum have got lucky and saved them selfs some money but across the lycoming fleet this will not be the case.