Is my upgrade screwed?

$75 off MSRP after 1yr of service, $150+ off MSRP after 22mo of service.

If you use the $75, you will not qualify for the $150 for another 22mo of service.

Wait the 22mo, get your bomb discounts, and call it a day. Or play around with other eligibility's on the account, or buy used online.
 
Also, in case you don't realize, the $150+ is because that upgrade also qualifies for any instant/mail-in rebates/savings as well. So, it's really $250+ when buying high end phones.