As has been said the best course of action is to go mechanical, especially as you can do it for less than the cost of a new sender. However if you are continuing with an electric gauge in my experience it is water ingress that causes problems. When I took apart a defective sender it was clear that water ingress had rusted up the innards. To help prevent this I suggest silicon around the terminal (there is a gap which allows water in). It is also beneficial to relocate the sender to a point out of the way of muck and water. This can be done by using a braided hose and if located higher up behind the radiator on the cross member where the steering rack mounts it will also reduce the vibration.