storing greenstuff

So I like me some greenstuff. However, as far as epoxies go, it's ridiculously expensive, especially here in canada. Sometimes I mix up too much for what I intend to use it for, say I'm gap filling some crisis suits and run out of suits to fill. Well what do I do with it? I don't want to waste it, even a small amount of it is worth it's weight in gold, especially when one is now on a budget.

I know cold makes it set slower, and heat makes it set faster - is it possible for example to freeze it and stop (or at least halt significantly) the time it takes to set? Does freezing affect the end quality of the epoxy?

There's always the possibility of mixing less every time I want some, but inevitably one messes up.

Nothing will stop the mixed putty from curing.