That's not accurate. I keep my iPhones for two years, and when I upgrade I give them to family members who have always gotten another 2-3 years of use out of them. (And Apple has continued to support them during that time with software updates.)

It's actually one of the main things that keeps me in the iPhone ecosystem.

That's strange, I still see iPhone 4s/5/5s on the regular. The lifetime of my iPhone is typically a year, yes, but my used phones live on for many more years through other people after I sell them.

Yes, 5 years of constant updates for every phone is so short, especially compared to Androids zero years.