I have been with Sky for 17 years and also only have a $50 saving.
I think their records only go back 15 years, they told me I sign up in 2009 when in fact I sign up in 1993!!
I found an email from 2007 but had it since 2005 or 2006. I wonder if they reset it if you change address. It also looks like might be missing out on other rewards which are based on length of service.
In any case I think I will wait to upgrade. It sounds like it is not ready yet. This is from the site when you go to sign up The following features are not currently available on the new Sky Box: Pay Per View, Sky Box Office, remote recording, closed captions and alternative audio. We are busy working on them and they will be delivered in subsequent product updates, for more information please see here