Became a new member very close to a signature series deadline.
Was able to overnight my comic in time, CGC was just busier than usual so my update was slow.
Another concern was the multiple submissions I had sent for a single book.
I was worried that my credit card would be charged multiple times but later found out that CGC only charges your account per book they have of yours in hand.
What I learned from this experience:
1) Mail your signature series comics early and in bundles when grading multiple comics. Saves on overnight and regular shipping.
2) When calling CGC and living on the west coast, call early. Before 1pm pacific time.
3) When calling CGC, call on a weekday. No phone operators on weekends from what I understand and the deadline I had was on a Saturday, so get all your info beforehand.
4) Double check your comic book labeling for submitting. Research accurately everything about your specific issue. A variant I submitted was actually released 2 months after the issue it's based on.
5) It's okay to mess up multiple submissions. CGC doesn't charge you unless they have your physical comic book in hand with accurate labelling printed and shipped by you. So don't worry about multiple card charges for one signed issue of whatever.
6) If you must overnight your comic, there's 3 options: USPS, UPS and FEDEX. Mail your comic to the CGC PO Box if using USPS. FEDEX and UPS delivery, mail to the communications parkway address.