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It depends on the importance of the glue joint in question, if it is a
mission critical joint, I always use a fresh tube. I'll still keep the
tube in hopes I can coax a drop out of it for common tasks though.

This sounds almost exactly like my plan!

If it's important, I open a new sacrificial glue.
If it's just some toy, I try the old stuff which invariably is all dried
up.