Review on Oatey Company 30374 1 7 Flux by Nathan Pintac

This tinned flux works well but every container I've ever used inexplicably becomes useless junk after about 14 months. It works fine one day, after a week or so it starts to discolor and turns into a weird dry brownish sludge over the next few weeks. There is no expiration date on the containers and no indication of "open life" so I have no idea what the issue is. It is also one of the best tinning fluxes available.