I presumed we were simply talking about the original Barn, not the '91 or '04 incarnation. And when it comes to the original Barn, we saw him in several different eras and he never once let his hair down, so to speak. Does that mean that we can state with 100% certainty that he would never ever change? OK - perhaps not. But to say that Barn was set in his ways would be an overwhelming understatement, and regardless of the era, much more likely than not Barn would remain "properly attired" in that era's style. For him to change, it seems to me that it would have taken a shakeup in his life that was analogous to a 100 kiloton dynamite explosion to break him out of his deeply ingrained habits.
If not a complete personality transplant! Though on a show like DS, the latter is most certainly not completely out of the realm of possibility.