I used Raka for my first nine projects, then tried US Composites on my canoe, and still working with that 3-gallon "kit" on my second Outer Island.
OI #2: http://mysite.verizon.net/NGC704/newOI/
Raka products and Larry Steeves have always provided complete satisfation. I only tried US Composites because it's a little cheaper, because Gerald seems to find it so reliable, and because it was just plain time to try something different I guess.
I got the slow cure, of course, and at first I didn't like it. It seemed to not want to set up as hard and/or reliably as the Raka I was so used to. But it finally came across that it was only a little bit slower in reaching a good first cure, and nothing more. In a word, Raka is hard as stone next morning every time, pretty impressive for a first cure, whereas USC is still a little green, and just barely sandable if it had been applied late afternoon the previous day. When I use the term 'first cure', it is acknowledgement that although epoxy cures in 24 hours more or less, it actually takes three weeks more or less to reach full hardness to what I call its final cure.
USC Pot life may be slightly longer than Raka, but not by enough to matter. Neither have ever showed any signs of amine blush.
The acid test for satisfaction is, as always, will I replace it when the time comes? Well, the jury's still out on that one; there are some things I like about USC and some things I prefer with Raka. And last time I talked to Larry, I mentioned that I had tried another brand of epoxy and without hesitating an instant he said "oh, that was a mistake". I'm still laughing at that, and believe I like the way he thinks about his business and products.
I'd have to say the chances are at least excellent that I'll go back to Raka. Very probable that I will, even.
One thing's for sure: it's a neck-and-neck horse race.
On shelf life: Easy 100% accurate answer -- do a small test sample. I'm betting it's okay.