All depends on how long you've had it.
If you plan on keeping it for a really long time, you might as well consider just getting a new one. Only because then you'll have to look into replacing the battery. If you can't do it yourself, then it's just more out of pocket expenses.
For example, my FR15 is about 4 years old and it gets used only for running every single day. I got LOTS of miles on it (over 5000 miles) and in the past few months the battery is just starting to notice some degradation. I was fortunate enough to find an exact replacement battery from an eBay seller in Germany. So I bought a new one and once it starts giving me more issues, I'll replace it.
After that, I consider the watch end of life, and time to buy a new one.
Was thinking of getting the Fenix 3 a couple years ago, but glad I didn't. The tech moved way, way, way too quick.
Waiting for it slow down still. Especially when my FR15 is suitable for my needs.