I agree with Haggis. I've had a fairly long beard for years, and the only itch problem occured the few times I shaved. A razor is rough on skin that's not used to it, so the irritation of shaving and the sandpaper feeling of having stubble starting by the next day was the uncomfortable thing.
Another point--beards grow in different patterns. On some people (I'm one of the lucky ones!) the edges end smoothly in a reasonably pleasing pattern. On other people, the edges will be uneven, or extend too far up the cheeks or too far down the neck, so to get an aesthetically pleasing beard, they'll still need to shave in places. Or they may choose to shave just to get a different pattern.
Like Parkinsonsd said, someone who's had a beard for a long time won't even really notice it, and just deal with the sweat and bits of hay in the beard same as they would in the rest of their hair.