[Bygracealone]

I wondered the same thing last year. It's weird that it says it can't be used again after opening. However, a couple of guys on the forum have stated that they've used it long after initial opening. You just have to seal it well while not in use.

I bought a tube of it last Summer and used it and then sealed the end by putting a screw in the tip. I plan to use it pretty soon, but I think it will work.

As for curing time, I'm not sure what to say. It does eventually set up and when it does it looks and feels sort of like rubber.