formula samples - when to sign up?

hi ladies!

i’m a FTM and i am hoping to be able to breastfeed, but in the off chance that doesn’t work for me and baby, i would like to sign up for some various formula sample boxes to have things on hand. i am due at the end of october 2019, so i am wondering if anyone else has signed up for these and when they received their free samples? i am looking at enfamil’s free samples and similac right now, but i know there are more. i just don’t want to get things too early and worry about them expiring before baby gets here.

thanks!