I recently had a blowout of my inner dual. Bought the tires in 2011, DOT code said mfg date of 2008. This one particular tire would lose air. Had it checked many times, valve stem replaced, and it would get soft after sitting. I'd check it every day during a trip and it would hold air, only to lose it when sitting. I guess it finally had enough after 4 years. It blew after a new valve stem change. I was going to give the tires another year but after that decided to replace them all. I do check pressures before and during every trip and other than that one tire, all seem to keep the proper pressure. Hope the new ones do, too.