In the interest of giving credit where credit is due, my avatar is a scan of a hand-drawn caricature by cartoonist Jim Naylor which was done at my company's 20th anniversary dinner.
I'd like to know how this works out (or has worked out for people). I definitely want to sleeve my destination cards, but I feel like sleeving the train cards would create a constantly falling-apart pile that just frustrates the hell out of everyone.
You are right - my sister-in-law sleeved her TTR (TTR Europe - so don't ask about sleeve size for TTR) and then unsleeved it because of this problem.
On the other hand, my train cards are starting to show wear and tear, and I find that pretty darned frustrating, too.
Since the Days of Wonder web store sells replacement cards for $5 I think that just replacing the cards if they become too worn is a viable alternative.