I am aware that excluding your companion's default you must provide ammo for them but I wanted to know if you companions weapons still degrade like they did in Fallout 3 when shot and used? Also does armour still have infinite durabilty when equiped to a companion, even if you give it to them?

Appeared so in my playthrough. Never had to repair any of their armor or weapons.

I've had to repair Boone's Combat Armor that I gave to him. I think it degrades very slowly though.

Hmmmm.... maybe I didn't keep anyone around long enough for it to be an issue... never seemed to have any trouble with Veronica's power armor or Pushy (when she had it).

Only larger weapons have the damager of damage by direct hit in combat, just like FO3.

If it's like FO3 they will degrade but at extremely slow rates.

No, definitely not armour. Remember how fast regular PA Mk-II degrade and you literally go farm Enclave for repair after exploring an area or two?

However I never see the PA Mk-II I gave Charon reduce in DR...ever