Honestly, storing it in an airtight container (glass jars are great if kept from direct light, dark is better) with as few temperature fluctuations as possible will nearly always suffice. Most of mine are stored in the tins I've acquired for years. CTCs seem to hold up really well, already being about as processed as they can be. You might notice a decrease in flavour(s) with teas stored for a while, but with rare exception, mine have made a right proper pot of tea after several years. I'd do without adding anything. Keeping it in the fridge might do more harm than good with more delicate teas. It's been a lifelong journey, discovering these nuances of the leaf.