Like all food and drink we worry that we have only a few days or weeks to consume something before we have to throw it out and get another. (We’ll leave for another day the fact that the practice is nefariously used by brands and supermarkets to buy more stuff).
Firstly, let us put your mind at rest. Gin will not go off. It will always be safe to consume, as long as it is stored with the top firmly on. You may lose volume through evaporation or indeed a bit of flavour over time but it will continue to safe to drink. As you know we recommend storing gin in the freezer to help cut down the usage of ice (link to G&T) but as long as you store your gin out of the sun light you’ll cut down these losses.
If your gin does start to develop an odd smell, flavour or appearance (remember unfiltered or barrel aged gins are supposed to be yellow) then we would recommend discarding it. But, this should not happen unless the gin was dodgy in the first place.