I sent mine in December 2018 and it was just delivered today. Long time. We thought they lost it or there was some problem we were unaware of. I was expecting a you didn't fill out something correctly form, didn't receive that just took a long time.
On another note I didn't realize that they want me to place four stickers on the car! My car is too pretty for four stickers. I'm seriously having second thoughts if it is worth it. I have fast pass already so not sure how much I'm going to gain by having diamond access that isn't already fast pass. Hmmmmm.
I bought paint protection film which I am going to attached the CAV stickers to. Cut it out to size then attach that to the body of the car. That way, you can take it off as a whole when the stickers expire. Otherwise, that CAV stickers are a pain to take off.