Do you ever worry about durability?

I do actually. And there isn't really a solution other than buying multiples of every figure you want, which to me is not a worthwhile solution.

It's doubly worrisome if you play with your figures. They won't last forever. And that's not a fault of Mattel. Paint will chip. Joints will loosen. No way around it.

Overall, I try not to think about it. It won't happen all at once. But it is kind of unsettling to know that these figures are not infallible (and that goes for the MOC ones as well).

Mine sit on a shelf, so long as I can give them a slight pose and they attach to a stand and stay there, that's all I need to worry about.

Yup
I haven't had any real problems yet, but my son plays with them and they are getting quite loose.
The ones I really care about though, I keep an extra one Moc

Definitely do. I don't play with the figs, they are just used for display and I've had several of the older ones just fall apart. Very expensive figs to replace now days. Legends 1 Dusty Rhodes, Legends tag pack Roddy Piper, earthquake..just to name a few.

I don't sweat it too much. I can understand a MOC collector being more fussed about it than a loose collector (like myself), though.

I've been collecting and displaying figures for 22 years now, and breakage (and shelf dives!) is just something you learn to deal with. My McFarlane (and early NECA) have become brittle and fragile over time...so I've learned to treat them like porcelain and keep super glue handy! A few of my McFarlane figures are made up of as much super glue as they are plastic at this point (I'm looking at YOU, Tortured Souls!). >.< My Inhumanoids all have hot glue holding their hips so they can stand up straight...and many of my vintage MoTU have gotten the same treatment. Some of my old figures (Super Powers, Visionaries, Centurions) are extremely durable, and are as solid today as they were decades ago.

So, when I get a new WWE figure, I add them to the display, hope for the best...and don't lose any sleep about possible future breakage. If it happens, it happens...cross that bridge when I come to it.

What they said.

every now and again i'll open one with a lose leg or something janky, but being in the game for a while you figure out how to fix small problems

Thankfully mine have never brok but some of my brothers have. I do worry though when in play as oppose to jakks which were more bulky and durable

I do. This is why I buy multiples of figs I really like.