Paul
I had all my maintenance done in Burley, ID at the Flight Doctor. Tim, Kevin and Brian kept up my 337 for 10 or 12 years. They did a great job and my rear engine had almost 2300 hours on it before we changed and installed a factory reman. They had no problem with signing it off because all the numbers were good. It was starting to use a little oil (1 - 2 quarts per 5 or 6 hours) so we decided to make the switch. Although the engine was still running strong. I have heard the same from others about over TBO.
http://www.theflightdoctor.com/