He was thinking 7

IPhone users are often looking for the charging cable, so it is almost essential to have a replacement, choosing a different shaped connector allows more opportunities. It's also handy to avoid twisting the original cable depending on the position or use of the phone.
This is my third iPhone cable, the original is at home, the angled cable I use to connect and store the phone in the compartment (cramped, that's where the orientation of the connector is very useful rev model only) of my car (Chevrolet Cruze SW system "MyLink"), and third (AmazonBasics Travel Adapter for iPod / iPhone 3G / iPhone 3GS / iPhone 4 Black) is in my bag for my business trips.
In my humble opinion, it is a minimum.