My yardstick is how long do you want it to last??

I will get a picture tomorrow of a piece of exterior ply I have in the shop. I was cutting out a piece to use as a form for laminating cockpits. It delaminated and half of it curled up like a potato chip.

Now this is a extreme but the quality of plywood (and wood in general) in the past few years is deplorable. I am all about cheap and dirty but if you want it to last, I would have to say pay the extra and shipping cost