What is the shelf life of Golfworks Multi-purpose high impact Epoxy ?. If when using product beyond its shelf life , what color will it be when mixed 1 : 1 ?? I just mixed some at a 1:1 mixing ratio, and it is gray in color … I really don’t know how long I’ve had the epoxy, but I was once told you can use the GW Multi-Purpose epoxy for eternity ????