Reservations necessary? How many reservations does one need and are they a necessity?

Preferred but not necessary. I have never made reservations at all and with the family pass you don't need to worry about not having enough time or it's to late to go.

Reservations are not necessary unless you are going for the VIP gondola. You can buy your tickets online or at the ticket booth out front of the ferris wheel, no matter where you buy your ticket they will not expire unless they are scanned. If you do buy them on the website you do not have to print them, just open the email and hit (print vouchers) when you get to the front of the platform and the loader will scan them off of your phone.