What item have you been using on a daily basis for the longest amount of time?
Sometimes I will use something and realize I've owned it forever. It's a nice change in our throwaway reality. I think my personal record is a bicycle multi-tool I got for one of my first bikes, ~25 years ago. Still have it, still use it. When it comes to electronic devices I have a Panasonic mini Hi-Fi from ~2005. Never felt like changing it.
A proper leather belt. I'm not sure when I bought it, but before that I only had belts that came with pairs of jeans, and a fake leather belt. They all felt uncomfortable, and the fake leather would split.
I bought a genuine leather belt and it's been fantastic ever since. The only signs of wear is the discolouration on the buckle, and the bend in the leather where I often buckle it.
I've been using the same belt since the late '90s. I recently lost a bit of weight so I'm in the market for a new one. It's tough trying to find a replacement for something that's been with you for more than half your life.
FYI - "genuine leather" just means the material contains some leather and generally indicates that it's the lowest quality.