When do pillows actually go from “fine” to “time to replace”?

It’s kind of wild how pillows don’t just “break” — they slowly turn into something else and you don’t always notice until way later. One day it’s comfortable, then it’s flat, then it’s just… there.

What’s confusing is the advice online doesn’t really agree. Some say replace them pretty often, others act like they last forever if you take care of them. But in real life, it seems way more subjective than that.

So how do people usually decide it’s time? Is it when the pillow loses its shape, starts smelling a bit off, or when sleep just doesn’t feel as good anymore? And once you replace one, do you notice a big difference, or is it more subtle?

Also if people treat different types differently (like memory foam vs. regular fill) when it comes to replacing them.