I have some Akzo left that is about 8 years old. With the price of Akzo these days, I don't want to throw it away unless I'm sure it's of no use. I mixed some up yesterday, prepped a piece of aluminum and sprayed it on. Looking at the result today, it appears as bullet proof as it did when it was new. Does anyone have experience using old Akzo? Should I use this seemingly good primer even though it is well beyond the expiration date?