I always buy a pair of shoe trees with every new pair of shoes or boots, so they have them all the time. On the other hand, a never worn pair may not require them, as I haven't seen any store that keeps their footwear with trees, except bespoke lasted ones.
Thanks Mercurio.
I had that case in mind.
At min 1:46 it's explained what I mentioned before ''most of the benefits of shoe trees happen in the next coming hours/days after using the shoes":
Said that, I am not sure if that also applies to a never worn pair that has been stored for years. I don't know if a shoe could get cambered in that case.