i deffenitely am a fan of sleeves but sleeves can get rather expensive depending on how many games you have i think i spent over 1000 $ in sleeves for my games but dam well worth it.
I also suggest laminating any character card or whatever gets used alot to protect from wear and tear also been testing out a product i used in animation its a spray on dull varnish type substance ( fixative ) i used it to fix the led to the paper when i was working with pencil or chalk or charcoal etc and im testing it on Doom Board pieces and Descent Board Pieces so far seems to work well it does not add to the thickness of the piece so it does not fit but rather gets sucked into the cardboard and once you let it dry coat it again and done.
I also have seen descent map pieces mad out of Dental plaster looks wicked and am considering testing it
Protect your games folks