" Are they actually durable or do they peel off after a few months? "

I cannot see them being durable at all.

Home Depot purchasers like the Smart Tiles Peel and Stick Backsplash

I contemplated it. Then I saw them in my friend's house and on the shelf at Home Depot and thought they looked way too tacky. Instead, I decided to have my backsplash primed and painted. We will see how long it holds up. I don't see why it won't. It looks really good, Much better than a stick on splash.

They have to be tacky. It's what hold them to the wall.

My daughters apartment has some sort of white peel and stick tile. From afar they look ok but close up they look like plastic and feel like plastic. I wouldn't want them in my kitchen. Where each tile section joins another you can tell as the the line that is suppose to look like grout is a bit thicker. Some of the corners are peeling up a bit.