Gin is a spirit flavoured with juniper berries and various botanicals, which can include spices, herbs and fruits depending on the manufacturer. It is the basis of many famous cocktails like Negroni, gin and tonic, Tom Collins and Singapore Sling, as well as the gin martini. It is distilled from a grain and has a very strong, dry flavour. Luckily, if you have leftover gin you don't need to worry about its shelf life, as it doesn't have a tendency to spoil.
Gin can be kept unopened for indefinite periods of time -- it has no expiry date. It will also keep well in the bottle with the lid on, however its aroma will fade in time.
As it is a distilled spirit, gin will not age in the bottle like wine does. Ageing causes changes to flavour and fragrance; gin will taste exactly the same whenever you open it.
Prolonging Shelf Life
Keep your bottle of gin away from direct sunlight and away from very high or low temperatures. If you've opened the bottle, ensure you seal the lid tightly. Better still, use a lid for wine bottles that extracts air from the bottle.
Gin is best kept at room temperature rather than refrigerating. Room temperature dilutes the alcohol slightly, making it more palatable to drink and a little weaker. If you're adding ice it will also make the ice melt more quickly, and the extra water can make the pungent flavour of gin easier to swallow.