A setup that actually works
The setup that works is boring: one opaque airtight container per roast level, a cool dark place to keep them, and a habit of buying amounts you will finish. Nothing else in the cupboard earns its space.
For everyday use, a tin with a gasket holds a seal better than a zip-lock pouch and is easier to open and close. Keep the original foil pouch for anything you are storing rather than drinking.
A vacuum sealer is worth having if you buy light oolong in quantity. A vacuum pouch at 5 °C will hold a light oolong for a year, which no tin on a shelf will do.
If you keep a lot of tea, a small dedicated box in a cool room beats a shelf in the kitchen. The point is to give the tea its own air rather than the air of whatever else is cooking.
Label the lid with the month you opened the tin. It takes about 5 seconds and it is the difference between knowing how a tea has been kept and guessing at it.
Keep the desiccant pack that came with the tea. It is sized to the pouch, it does real work in a humid month, and throwing it away removes a free safeguard.
Where to put it
The best position in most homes is a low cupboard away from the oven, the kettle and any window. Heat rises and light comes in, so the two worst places are the top shelf and the worktop.
A cool room that is used for something else is usually better than a warm room used for nothing. A bedroom cupboard or a hallway cupboard at 20 °C will outperform a decorative tea shelf in a sunny kitchen.
The fridge is a good home for sealed light oolong and a bad one for roasted oolong. If you use it, keep the tea in the body of the fridge rather than the door, where the temperature swings every time it opens.
Avoid the freezer unless you are storing vacuum-sealed leaf for years. Thawing and refreezing moves moisture through the packaging, and a partly used pouch that goes in and out is worse off than one kept on a shelf.
A cupboard under a worktop is usually the best spot in a kitchen, because it is low, dark and away from the kettle. Aim for somewhere that stays near 20 °C all year rather than somewhere that is cool only in winter.
If your only cool space is a fridge, use it for light oolong in vacuum pouches and keep the roasted tea elsewhere. A vacuum pouch at 5 °C will hold a light oolong for a year, and half a regime beats none.
Mistakes to skip
The first mistake is a clear container. Glass looks right and does nothing to stop light, which is one of the two things a container exists to block.
The second is a large tin that is opened often. Every opening exchanges the air inside, so a 500 g tin used daily ages far faster than five 100 g packs opened in turn.
The third is mixing roast levels in one container. Roast travels through the air between leaves, and a light oolong stored with a roasted one will pick up the roast within weeks.
The fourth is trusting a seal that has worn out. Zip locks and gaskets both degrade, and a container that held a seal when it was new may not hold one now.
The fifth is buying storage before buying tea. A cupboard of empty tins helps nobody, and the container should be sized to the quantity you actually drink rather than to the quantity you imagine buying.
And do not store tea in the fridge door. The temperature there swings by several degrees every time the fridge is opened, which is exactly the instability sealed leaf does not need.
Check in often
Check the tea rather than the container. Open a tin once a month, smell the dry leaf, and close it again. A roasted oolong should smell of roast and stone fruit, not of dust.
Check the packaging at the same time. If a vacuum pouch has lost its vacuum, the seal has failed, and the tea inside has been breathing for however long it has been that way.
Check the light level in the cupboard once, in the middle of the day. If you can read a label inside it without turning a light on, the tea in there is getting more light than it should.
Check the quantity against your drinking rate twice a year. Most storage problems in a home are really buying problems, and the fix is a smaller order rather than a better tin.
If a tea smells tired at the monthly check, drink it over the next month rather than saving it. 2 years of careful storage cannot rescue leaf that was already fading when the tin was opened.