we now have lots which will last us for many months. Although if a specific tea stands out I may buy more to keep in stock. I also have a lot of unopened 'taster' sized pouches from NBT.
I opened a tin of tea I bought in Harrods 28 years ago and drank it a couple of months ago. It was absolutely fine.
I suspect that tea, kept dry and cool, has quite a shelf-life - way beyond what my consumption rate would mean that it remains to be used.
As TE folded, they had commercial orders cancelled as cafes, restaurants closed during lockdown. They offered a Darjeeling second flush from a large cancelled order (I am no huge fan of first), at crazy cheap prices - it is one of three that get brewed most often, but it will last at least 2 years in total.
I must get back into the habit of having a green tea on the go all day...... I used to take them into work as they require no milk so were very convenient. I have been working from home for at least 4 days each week since the first lockdown.