the bats are returnable if you have a valid receipt. some mom and pop shops still have old bats on hand. if they are authorized dealers, they can sell them with valid receipts still and returns will be honored. at the local sports store here, I seen a easton SCN6 which is from 2008. if i were to buy it today and it broke within 400 days, easton would still honor it, but they would probably call the store to verify since these cases are not the norm.
in your case, no. you can not return your bat that was bought 4 years ago and return it with that 4 year old receipt. unless it had a lifetime warranty like some models have had in the past. like the decker enigma