Hi Snadger,
Most gin/vodka is round about 40% alcohol, I don't think that there are any commonly occuring microorganisms that can live in that so fermentation is not going to happen. So don't worry about bottles going bang. Many years ago a boffin type mate of mine did start to explain what happened chemically but after about the third glass I completely lost interest in anything except whether he was going to shut up and pour!!!!

Compo