Shoulder Pads DO NOT Expire

As for people saying it's pointless to get these shoulderpads because better ones are coming out, I say you're silly. That's like saying it's pointless to get a new weapon right now because you can make one soon with the new chaos profession systems.

And I'd say that anyone heavily investing in new weapons right now is rather dumb for precisely that reason.
Much like those who continuously made Red Katanas were silly considering that Pyropes were right over the horizon.

That said, I wouldn't blame you for getting the shoulder pad now if you're doing the Cake v Pie anyway.
If you could still get White Scrolls, then, yes, it'd be quite ludicrous to get the Shoulderpad instead.