I lied my Exiles are also not metal but seem sturdy, I don't believe you should have any issues with the materials snapping. The only way I could see snapping occurring is due to pressure in the base plate due to over tightening the screws...
I put 50+ days of hard shredding on my Cartels and the only thing I've had issues with is one of the ankle strap ratchets (bent mounting bracket from a nice wreck). Good binding IMO, I definitely enjoyed mine, but there are other options out there. Why not take a look at some Rome Targas or Ride Alphas? They're both comparable to the Cartel and Force SL.
Would I pay $50 more for the Unions? Probably not, I never jumped on the Union bandwagon. Would I choose the Cartels instead? Maybe, but not after looking at all my other options.
Having rocked some Cartels for a couple years, I hated them simply because the parts were constantly breaking and the toecap slipped. They've changed the toecap since then, but not sure about durability.
If you don't hop on it, I'm not talking to you anymore since there is no hope for you. Mmmmm... Rome 390 straps... Mmmm... Canted footbeds (3 for each binder)... Freestyle flex.... Rome customer service.... Effin DEEEELISSH!
I currently have a pair of Cartel's that are about 4-5 years old, bought them off craigslist for $50. They seem to work good for me... but I don't have much to compare with. My previous bindings were over 10 years old, made by RED (Burton subsidiary) that doesn't even make bindings anymore.