Two thoughts on glue:

 

I rarely have spoiled glue, and I keep it out on my bench for weeks at a time. There are two things I do consistently, though. One is that my outer and inner pots both have lids, and I always put them on while the pot is still hot, on the theory that by doing that I can prevent anything growing that can't live at that temperature. Anything that comes in later will have to come through a double wall. The other thing I do is before I close things up, I put a bit of alcohol on the glue, to steralize anything I can. I've kept glue for longer than a month this way. When the glue is heated, I always check it by taking a drop between my fingers and pushing them together and apart until it dries, to judge the stickiness. If it's not up to par, I toss it. Bacterial degradation can be noted in two ways: it starts with tiny watery pits in the surface of the cold gel; after it's gone a ways, all of the hard glue will be less hard and have a skin of water on it. Either symptom means you should toss the stuff.

 

Second, I have learned that contrary to my intuition, I really do get better joints if I warm the joining surfaces of the wood up with a hair dryer or alcohol lamp before gluing. I was skeptical of this for years, but finally realized that it has a definite positive effect on centerseams. The Cremonese makers scratched diagonal scratches on their top and back seams, possibly in the mistaken opinion that this gives a mechanical bond, but more likely what it really does is limit glue squeeze-out by throwing up tiny ridges, but whatever, I do this also, and it doesn't hurt, at least.