There was one "unused character wipe" done sometime in Late 1998 or so. I lost some on one account then. But if you closed your account any time since then, your characters will be there - with backpacks and bank boxes full of the items you stored away. If it has been well over 90 days, then any houses will probably have fallen.
The only exception to this rule would be if a friend had access to the account, or it was hacked and reactivated. Then someone may have intentionally deleted your characters.