> Someone mentioned that RFC in our Cisco switches could be the problem.
RFC is set of published documents, representing miscellaneous de-facto standards. There are lots of them and you should ask what exact RFC (or a list of) do they mean. Only then use google to find them all.
> We have a Polycom video system that times out after about two hours.
Hardly it’s a Cisco switch problem. Your network may be misconfigured or overloaded, but it still not the Cisco problem. Your videoconferencing equipment may have bugs, memory leaks, misconfiguration or something else to cause this timeout. I recommend you to ask Polycom vendors or even hire consultants/analysts of the problem is not in Polycom.