My Nexus 5
I have had my Nexus 5 since December 2013, two months after it was first released, and I still love it. I have no intention of replacing it until it is completely dead.
I think it is a beautiful phone. It still runs quick and the battery lasts around a day and a half, depending upon usage. I accidently cracked the bottom-right of the screen when it went in my cycling saddle bag. The power switch occasionally bugs out and needs a good smack on a hard surface. It collects a ton of dust in the speaker holes and the case is cracked from where I have dropped it. These are not reasons to replace the phone, but rather modest proof of a well-used piece of equipment.
You do not need the latest and “greatest” smartphone. If you look after your phone and it serves you well, why pay money to upgrade again? You only need something that will do what you want, and not what other people want you to use it for.