Assuming that you allow your bottles to naturally carbonate, which requires 1-2 weeks at room temperature, storage should be cool as a minimum but cold is best. The cooler the storage temperature, generally the longer the beer will last or stay "fresh" tasting. If you have some bacteria in your brew, and we all do to some extent, low temps will help to inhibit the bacteria. Oxygen absorbing bottle caps also help to extend the useful life of your brew.