I use my phones for trade-in credit or as donations (mostly as donations, before I bought my Note 3 I only had low-end feature phones and mid-range Androids)
I'm only on my second tablet, I gave my first one (a G1 Nexus 7) to my mom.
When I start retiring my current lineup, I'll probably start selling. Apple products retain their value fairly well so I've kept all the boxes, containers, etc. to help with that.