brjr51, this thing was about half as long when I started. Every time I post it someone comes up with good issues I need to add. I have had a lot of filler set around for years with no problem. But If I remember there is MEKP in it and fiberglass hardener (MEKP) definitely does have a shelf life. You do not want to use anything over a year or so. In fact, the fresher the better.

But I do have something that comes to mind; Always and I mean ALWAYS knead the tube of hardener. If some watery liquid comes out into the "bondo" remove it and knead the tube better. I have had strange things like the "bondo" not hardening when that watery stuff is seen. I have no scientific backing as to why this little amount of liquid would cause such trouble but I have seen it too many times to ever let it happen again.

1948 Chevy Pickup
Chopped and sectioned
owned since 1974 when I was 15.