I have been running my IO-520 engines to a 2000 TBO for the last 20 years. Each and every engine has been within manufacturers specs after retirement. This was proved, and documented, by the very reputable engine shop that I used for overhauls. Our engines fall into the, "more than 40 hours per month", category. Fortunately we recently purchased two engines direct from the factory due to the strong Aussie dollar so we wont have to rely on our engine programme to get the 2000 hour TBO and can now extend to 2100 hours under the OEM instructions. Happy Days I say.
Groggy