As stated above the brass will not rust out but most hear that they won't hold in the block tight , leak or pop out. Proper installation is the answer. Most guy's use the easy method by inserting a socket into the center cup and then pounding it in. This method pulls the sides of the cup in reducing wall tension needed to hold the freeze plug in. Proper way is smear some sealant around the outer freeze plug and tap the outer rim to insert it flush with the block. There might even be a proper tool .