The Wein will not last nearly as long as the old mercury cell. Depending on local weather, it will last from a couple of months to a year or slightly longer.
Originally Posted by LeonardT
Save the washer ring from around the Wein cell, it will slip off with some force. Then replace the Wein battery cell with a 675 zinc-air hearing aid battery, available at your pharmacist or local convenience store. The 675 will just slip into the Wein washer. The hearing aid cells are much cheaper than the Wein cell, probably 6 or more for the price of one Wein cell.