If the batteries were easily replaceable, and the software didn't continually get bloated, and companies kept issuing security patches, sure.

I kept my last desktop system for 10 years. Actually I still have it and it performs sort of ok (I was running Mint the whole time). But I upgraded and the performance improvement was actually worth the considerable cost. I've gotten similar life out of my other desktops and laptops over the years.

I think at least 5 years or preferably 10 is reasonable for smart phones.