You mean air tight, right? I do think air tight (or nitrogen filled) and keep in cooler temperature help. Many good tea stores refrigerate the green tea. I personally won’t buy it longer than 1.5 year. “sous-vide” implies adding heat – which is not a good idea for storing tea.
“Although from the packing of Ming Cha, the leaves are just packaged in a tin can with air contact.” <-- there is probably another bag inside – I hope so. If not, then don’t buy it. If not, the tea won’t even last 3 months. Not at that high price level. US $200 for only 25 gram, and one year old. No way. But I do honestly think there is another airtight bag inside the canister. By the way, if you have the money and really like Dragon Well, I will say that MingCha (store) is sourcing in high quality Lion Peak tea. Remember I said that there is even distinction among tea within the Lion Peak region? MingCha is sourcing the better one among Lion Peak.
Both white tea and Pu erh can be stored.
Green Spring Spires is good. My grandmother most favorite tea. I think at the end it is personal taste. I would say different in my opinion. Different enough that most people can distinguish the taste.
“(although I don’t think they will show you the top pick Dragon Well for free”
That would be true for any tea shop for any expensive tea for that matter, otherwise random people just go in and sample all kind of expensive tea. Business practice.
I think Top Pick can mean very different thing than First Pick. First Pick has a real definition that it is the first harvest of the first tea leaves. No one can misrepresent it. Top Pick just means the store or the farm consider these as their top selections. So I would say beware what they really mean. Their Top Pick may be same as First Pick, but it may be something else.