I'd think you'd have to be really, really good to be able to go back and forth on various clubs and still hit them well. Heck, it's hard enough to hit any 14 well all the way through the bag.
I think it is a lot more difficult than it used to be to get a "perfect" set and stay with it, though, because of the extra options now available in wedges. If you carry 4 (or even three) wedges, you are almost condemned to gaps somewhere in your set, and they tend to be on the long end of the spectrum. Switching around from hybrids to fairway woods to long irons, etc., has become a lot more prevalent.