I can't comment on the long-term durability of the T3PA pedals, but I had a Thrustmaster Ferrari F430 Force wheel prior to my current T500RS, and the F430 pedals were pretty much identical to the stock T300 and TX pedals. I haven't done a direct firsthand comparison between the TX pedals and the T3PA Wide pedals yet, but I'm pretty sure the T500RS pedals are identical to the F430/TX/T300 pedals but the T500RS pedals are all-metal (including the pedal arms). I've since passed my F430 wheel on to a friend, so I don't have those pedals on-hand to compare to the TX/T300 pedals, but I feel confident in saying I don't think there's a difference in between the F430/TX/T300 pedals.
Similarly, I'm pretty sure the T3PA pedals are identical to the T500RS pedals, except the T3PA Wide pedals are all plastic (except for the pedal pads) -- so that would mean that the pedal arms on the T3PA Wide pedals are identical to the F430/TX/T300 pedals.
This all makes sense, because if Thrustmaster came up with a good design for the pedal arms that can be produced in either metal or plastic, they didn't have to invest a lot in reinventing the wheel -- a good design can be used on multiple products to keep engineering/design costs down.
That speaks well for the F430/TX/T300 design in general, and also the T3PA Wide pedals.
Now, that said, I have seen a failure with the plastic parts -- specifically, the arm for the brake pedal on my F430 pedal set broke (the plastic cracked and broke, making the pedal unusable). Thrustmaster replaced the entire pedal set under warranty and the replacement pedals gave me no further problems, but they didn't get much use from me after being replaced because I moved to my T500RS setup shortly after that.
So, I can say that I have witnessed a failure of the plastic pedal arms on the F430 pedal set, which would seem to indicate that perhaps the plastic arms on the T300/TX (and maybe T3PA Wide?) pedal sets are a bit less durable than the metal counterparts on the T500RS/T3PA Pro pedal sets.
Just something to think about -- when I have a chance to do a head-to-head in-person comparison of the T3PA Wide pedals and the TX pedals (which I have on-hand), I will report back on whether there are any differences, and I will try to take pictures if I find any significant differences.