Being professionally operated, the engines have never had any cylinder cracking in their past. As mentioned previously, 2+hr legs were the norm for the aircraft thereby minimizing heat/cooling cycles on the engines and enhancing their chance of making TBO.
With regular use, these engines could go to TBO (1500 Hrs/12yrs) and beyond.
See this article to read up on TBO's and engine useage! TwinCessna Flyer article below says that this engine, the IO-470-VO is a TBO Buster!
http://www.twincessna.org/tbo.pdf
The propellors are Hartzell 3-blade propellors. TBO is 2400 or 72 months, whichever comes first. The props are at 1200 hrsTSN and 10 years.