I have bought, sold or traded in lots of nearly new iphones, iPads, Macbooks, Macbook Pros, Apple watches with good experience over many years.
Older stuff is more of a lottery.
I have been able to get Applecare without problem on stuff less than year old.
Trade in values are pretty good.
Their pricing is sometimes inconsistent, resulting in some good bargains.
If you buy on line you have a no quibble 14 day return period.
Everything has a two year warranty.
I find the instore experience unpleasant, queues, noisy.