Struggling with a decision regarding the Go 5G Next Plan and Upgrades

So today I tried to trade in my Pixel 7 Pro for a Pixel 9 Pro based on the promotion taking place right now. The guy at the store said that my phone was in pristine condition and definitely qualified, but before I could upgrade I would need to switch to a Go 5G Next plan for $20 more a month. Most of the features I'd get (Netflix and increased hot spot data) are things that I would never use. However, I ran the numbers and in exchange for giving them a roughly $300 used phone and paying them $20 more per month indefinitely, I would be getting a $1000 phone. It would take about 35 months before I started losing money on that deal. And in 24 months, I would be eligible to upgrade my phone again. HOWEVER, I'm worried that in 2 years the phone will have sustained enough wear and tear that it won't qualify anymore. If that's the case, I would probably end up losing money. Does anyone have any experience with this?