I've been smoking a pipe for about 33 years now, and I'm still always open to trying new blends. Of course, I do have favorites that I always keep on hand -- I have over 80 different blends in the cellar that I know I really enjoy -- but I've almost always got an open tin of something new as well. Sometimes I like the kind of concentration that I feel new-to-me blends deserve; you know, those times when you're really focused on trying to figure out what's in a blend, how well it smokes in various pipes, how it changes -- or doesn't -- as you move down the bowl, what difference drying might make, and whether or not I'm actually enjoying it. Other times, I just want the comfort of a known friend.
BTW, I'm always rotating through 5-6 open jars. (I keep all my tobacco in the original tin until I'm ready to smoke it. Then when I open a tin, it goes in a jar for smoking over the course of the next month or two.) I can't imagine having only "one or two" favorites, though, since I enjoy about five different styles of blend (English, Balkan, Virginia, Virginia/burley flake, aromatic) and one specific blend that I always have "open": Penzance.
Bob