I keep it in my shop and generally use it when I'm doing pen kits or whenever I need something that will stick to metal. As others have noted, moisture accelerates the curing process, and wetting one side of the joint is helpful (but not required). When gluing pens, I run some water through the hole in the blank,and then apply the blue to the tube.
There are a few downsides. First, as others have said, it expands as it cures. That's fine but the application may require that you control how/where it expands. Also, the expansion is a foam that doesn't have a great deal of mechanical strength. When gluing pen tubes, understand that the expansion can actually shift the tube out of the blank. A clamp, or even masking tape across the end of the blank, will hold the tube in place.
Second, the stuff seems to get all over your hands, and it's miserable to remove. I wear rubber gloves to simplify cleanup.
Third, it will slowly cure in the bottle. I've gotten into the habit of buying small bottles because if I buy the large, economy size, it will go bad before I can use it.
