Short-term: hold the freshness
Short-term storage is about holding what the tea already has. For a light oolong that means sealed, opaque and cool, with the goal of drinking it within 6 months of packing.
The enemy in this window is aroma loss rather than spoilage. Light oolong aroma compounds are volatile, and every opening of the container lets some of them out.
The practical approach is to keep the working quantity small. A 50 g tin you open daily does far better than a 250 g one, because the surface area exposed to fresh air each time is smaller.
Re-seal properly every time you pour. A pouch left open overnight loses more aroma than a sealed one loses in a month, and the habit costs nothing to keep.
Roasted oolong also has a short-term phase, but it points the other way. A freshly roasted tea needs 1 to 3 months of rest before the fire note settles, so the short term is a period of waiting rather than of protecting.
Long-term: change the goal
Long-term storage means accepting that the tea will change. For roasted oolong that change is usually an improvement: the roast softens further, the cup gets rounder, and the aromatics move from fire towards fruit.
The conditions are the opposite of a fridge. Sealed, opaque, room temperature, and left alone. Interfering with a tea that is settling well is the most common way to spoil it.
Aged oolong is the deliberate version of this. Leaf is held for years and sometimes re-roasted along the way, and the result is a tea that tastes closer to an old red tea than to a fresh oolong.
Light oolong does not have a useful long-term phase. Held for years it does not become aged oolong, it becomes dull oolong, and the money spent on it would have bought better tea fresh.
Sealed, dark and left alone are the three conditions that matter. They are also the whole long-term method, and interference is the main way people spoil a tea that was doing fine on its own.
Temperature is the setting that changes with the goal. Cool for holding, room temperature for settling, and steady for both. In practice 5 °C and 25 °C are the two ends of the range you will actually use.
Which is your case
Your case is decided by the tea rather than by your intentions. If you drink light, green-leaning oolongs, you are always in short-term storage, whatever you tell yourself when you buy in bulk.
Someone who drinks charcoal-roasted oolong or traditional roast Tieguanyin is in long-term storage whether they planned to be or not. Those teas hold for years and improve for months.
If you drink both, you are running two regimes in one cupboard. That is workable, but only with separate containers and a clear idea of which tin holds which.
The awkward case is a medium-roast oolong bought in quantity. It is stable enough to keep and not roasted enough to improve much, so buy it in the size you will drink within a year.
Roast level is the honest test. If you cannot taste roast in the tea at all, you are in the short-term case whether you meant to be or not, and the tea should be treated as a fresh one.
Medium roast deserves its own note, because it is the middle that catches people out. It holds for about a year and then stops improving, so it rewards a modest order size rather than a bulk purchase.
A quick decision rule
A rule that covers all of it: match the quantity to the window, and match the window to the roast. Light oolong, 6 months. Medium roast, about a year. Heavy roast, as long as you like.
Then use one container per roast level and put the month on the lid. Two pieces of information, and they answer almost every storage question you will actually have.
If you are unsure which case you are in, brew the tea and decide from the cup. A tea that still tastes of fire is in its settling phase; a tea that tastes round and quiet is ready to drink.
And when a tea is at its best, drink it. Storage is a tool for keeping tea good, not for keeping tea indefinitely, and the best cup is usually the one you did not save.
If you are still unsure, buy 100 g rather than 500 g and see how long it lasts. Your real drinking rate is a better guide than any general rule about how long oolong keeps.