Sloe gin tastes better as the time goes on. Last Christmas I was making a venison casserole but silly me didn't read the recipe to make sure I had all the ingredients. I needed red wine but didn't have any but I had a bottle of homemade sloe gin. I put some of that in it instead and it was delicious. OP, that reminds me I have a bottle of blueberry gin hiding in my wardrobe. Might give that a go tonight.
Of course, anything with that high an alcohol content will last for a very long time! Mine often stays around for a couple of years, the only issue is if the fruit is still in it can go cloudy, but that doesn't affect the taste or safety.