The short answer
White tea is the clearest case in tea of a category where new and old are both correct answers to different questions.
Fresh white tea is light, sweet and floral, and it is at its best in the first year or two after picking.
Aged white tea is darker and thicker, tastes of dates and old wood, and is a genuinely different drink.
Both are real, and neither is a better version of the other.
If you want to drink it this year, buy fresh White Peony or Silver Needle.
Keeping something means Shou Mei, and it should be pressed.
Grade decides which way to go. Bud-heavy teas are at their best young, and leafy ones age better.
Silver Needle ages, but the change is subtle and you have paid a great deal for the starting material.
Shou Mei is the cheapest of the three and the one with the most to gain from ten years in a wrapper.
So the answer is not new or old, it is which grade you are pointing the question at.
Three years is young for an aged white, seven is where it becomes interesting, and fifteen is a long storage.
Why age matters differently
This is the least processed tea there is: picked, withered, dried. Nothing stops what happens next.
What happens next is slow oxidation, and it continues for as long as the leaf has moisture and air.
In a bud-heavy tea the effect is small, because there is little surface area and little of the material that changes.
In a leafy tea with stems, which is what Shou Mei is, there is far more of it.
The result after about seven years is a darker, sweeter, thicker cup with the floral note gone.
Below about three years there is very little difference, and a cake sold as aged at two years is a young cake.
Pressed white ages faster than loose, because compression brings the leaf into contact with itself.
Humidity drives everything. Around 60 per cent and the tea develops, and much below that it simply sits.
This is the same mechanism people describe in pu-erh, and it is slower and gentler in white tea.
What it does not do is improve without limit. At some point it stops developing and starts to thin out.
Pressed white is a recent format, so a cake from 2010 is about sixteen years old at the outside.
How to tell
Ask for the picking year and the pressing year separately, because on a cake they are usually not the same.
Look at the leaf. Fresh white is pale with visible down, and aged white is darker with the down worn down.
Smell it. Fresh smells of hay and dried flowers, and aged smells of dates, wood and sometimes a little medicine.
A sour or sharp note on an aged white means it went damp, and that is a fault rather than a stage.
The liquor also tells you a great deal. Fresh is pale gold, and aged moves towards amber and then deep orange.
Break a cake and look at the interior. It should match the surface, and a pale middle under a dark outside is forced.
Pressed white only became common around 2010, so a cake said to be much older than that is not.
Taste is the real test: aged white should be thicker and sweeter than fresh, not merely darker.
Buy the same tea fresh and aged from one seller and drink them side by side. Everything else is reading.
Price is a poor guide, because aged white is priced on a claim that is hard to check.
Fifty grams at 3 grams a cup is roughly 16 cups, which is enough to compare two sellers side by side.
Storage caveat
Aged white only works if somebody stored it properly, and much of the cheap aged white on the market was not.
It wants a stable humidity around 60 per cent, a stable temperature, and no strong smells.
Guangdong storage is warmer and faster, and it produces a heavier, darker tea in fewer years.
Dry northern storage is slower and preserves more of the original character.
Neither is wrong, but they produce different tea, and a seller should be able to tell you which you have.
At home, a spare room beats a kitchen, and a kitchen beats anywhere near a radiator.
Too damp and the tea goes sour, too dry and it stops developing. Both are common and both are invisible until you open it.
Keep the wrapper, since it carries the year and it protects the cake.
Check cakes once a year by looking and smelling rather than by unwrapping them entirely.
If a cake smells musty at the wrapper, the storage failed, and no further years will put that right.
Sixty per cent humidity is the figure to aim at, and a hygrometer that measures it costs very little.