I know some other VOIP providers that would keep me on hold until I was old and grey, but I won't mention them here! Dell seemed to be good for that when I called them too.

Anyway, my wife talked to her mom for 55 minutes without getting cut off, so it is very random. Perhaps it is something from an upstream provider or something? Depending on the call route, maybe one of VOIPo's providers does something with the session timers.

Somewhere in this forum I think I remember a patch someone created, a backport from Asterisk 1.6 to 1.4 to support the session timers. I'll dig for that.