Why does the glue in a puncture repair kit dry up so quickly? With puncture repair kits, generally you get like 6-8 patches and a tube of glue.

The only problem is I can really only use the glue for the first patch because once it opens, it just ends up drying up. Am I putting the lids on wrong or something?

I have plenty of the patches left. It's pretty much the glue that makes me keep having to buy more kits. Why do puncture repair kits only have one tube of glue? Is there anywhere where I can buy just the glue in bulk?
In my experience:


You only need to apply a drop of glue a bit larger than a pea (about 7mm diameter) per patch;
Glue inside eventually dries. If you only have a puncture once a year, most probably the glue remaining from the last puncture would be dry "no matter what". Also, there is an expiration date of around two years, but I think it's two years if you didn't open it yet;
(IMPORTANT) When you attach the cover of the tube, BE SURE TO REMOVE ALL THE AIR INSIDE by pressing its bottom untill half a drop shows up in the opening, otherwise the glue will evaporate inside the very tube (happened to me a lot of times until I figured it out...).
These glues have a volatile nature. I wouldn't buy it in large amounts, but rather to buy new spare glue tubes (without the whole patch kit). The kind of patch I use also have this problem: the patches (a small roll I have to cut with a scissor) last much longer than the glue.


Well, hope it helps!