Mine's been rolled up and tossed in the trunk of my car, between games and the occasional dog mistaking it for a bone and trying to carry it off and bury it. They're pretty darn tough.
Mine is Chessex, BTW. I find that if you wipe it clean after each session, it'll last pretty much forever. No special care needed - certainly not laminating it! I'd be far more afraid of destroying it by trying something like that than by mere neglect.
If water doesn't take the marker off, try Windex. That will take most any mark off pertty well. I've noticed that on Chessex mats, it will also slightly fade the printed lnies, but you'd probably have to clean it with windex every day for a year for it to be an issue. The Crystal Caste ones are a little more forgiving that way, but on the other hand the marker ink doesn't show up as nicely as on Chessex.
BTW, Chessex now has a 4' x 8' reversible mat. $99.95 at Games Plus. I feel like the kid from Christmas Story every time I go in there and walk past it...