I used my Oneplus 6 for about that long and moved to lineagos after updates stopped before retiring last year. Phones are getting more powerful while the app demands aren't really increasing, so I think 7 years isn't that outlandish now days.
There's people who only use basic social media apps and do phone stuff, so phones don't go obsolete fast for them unless they are chasing the newest camera improvements.
I was using my OnePlus 6 for about 4 years before I got a stupidly good deal on a OnePlus 9. Wasn't planning on upgrading but here we are. I felt no real reason to update as it was still performing well except the battery. I'm probably going to keep my OnePlus 9 for about as long.
Sure, this isn't the norm but my guess is more and more people are going to keep their phones longer now that the price is so damn high.