"Sacha Hubbard" wrote
Just a bit of mild curiosity and a small personal survey. ;-) What does
the panel think is a reasonable time in which to take back a dead plant
and
expect a replacement?

I've taken back a dead tree for a refund, a few months after its purchase.
I've also returned a dead tropical fish (I sound like John Cleese!). My
local garden centre has a year's guarantee, which I always forget about, and
I never keep the receipts. However, if the plant was fairly expensive, I'd
probably return it anytime up to the end of the year's guarantee.