[bigeasy1]

I work for a friend in the marine fiberglass supply business,and hear all kinds of complaints about resin purchased from big box stores.
Polyester resin has a fairly short shelf life,especially when it's exposed to warm temps or sunlight.
Most of the big box type stores whether they be Home Depot,Lowes,or west marine don't sell as much as you'd think when it comes to resin.Also,the stock does not always get rotated as it should.
There is a big difference in quality between "cheap so called boatyard resin and higher priced resins.Beware of the el cheapo stuff.It's cheap for a reason,(it's junk).

In the case of Home Depot,Lowes,and other home center joints,the quality of the resin is also questionable.
You are far better off buying resin from a supplier who specializes in it,as most of us on the site do.

If you have to buy it in a pinch,I guess it would be best to get it from one of the boating stores.Even then,it's quality and freshness can be suspect.
Before you use it,try catalyzing a couple ounces of it,to be sure it kicks.

We get resin in bulk which is dated,and we repackage it in containers that move out of inventory very fast.We never have resin sitting on the shelf for longer than a few days or a week or so.
I've used some polyester resin when I actually had to strain it from the gallon because of lumps in it from sitting around,but it did cure ok.

In between uses,store it in a dark cool place out of the heat and sun,it will last much longer.