Sorry, I'm going to call BS on this. You aren't always on a "regular route", depending on your type of operation it's entirely possible that you're on a route that neither you nor your fellow pilot have flown before. For me, it happens more often than not, but that's the nature of operations at my particular employer. I am very pro-active about having enroute charts out, reading the frequency information and generally trying to stay ahead of the game. But the reality is that the Jeppesen high altitude charts do a relatively poor job of depicting what frequencies cover what areas and when you might expect a frequency change, at least within a single FIR. There's usually enough information to determine what frequency to expect crossing a FIR boundary. I fly plenty of places where if you aren't familiar with the route, there is simply no way to predict when you'll be out of range of your current frequency, or what the next one might be.