I think almost all of us use powerheads and they are built very well and last a long time, but sometimes we throw them out before their time. I don't remember how old my powerheads are but I think they are all at least 20 or maybe 25 years old. I have no recolection of buying them, but I'm old.
This one ran my DIY skimmer and it was placed behind the rockwork so I never pay attention to it. I had to shut it off last week to change around some wires and it didn't re start. This is how most powerheads fail.
The steel shaft on older powerheads are chrome plated and they do not last forever. Newer powerheads use ceramic but even those have problems. The hole the shaft sits in in the base of the powerhead is a hole with no special treatment to the plastic in that area so eventually the hole enlarges causing the magnet that revolves to hit the sides of the enclosure. The hole through the center of the magnet also enlarges over time causing the same problem.
These things don't last forever especially in salt water.
Usually they are very easy and almost free to repair.
All of my powerheads have a piece of shrink tubing over the shaft.
It costs about a nickel and takes seconds to install. You can get heat shrink at Radio Shack. I just slip it on the steel or ceramic shaft and it takes up the space that was worn away from the center of the magnet and the "bearing" holes in the housing. This does not look like it will last but the design of powerheads allows water to enter and lubricate the shaft so the plastic shrink tubing lasts for years. And when it wears out, I just install another one.
I have never bought a powerhead since these were first installed and they all have had the shrink tubing repair many years ago.
You can see the white shrink tubing here.

Getting back to powerheads, this one is on my (tiny) goldfish pond and most mornings I would have to bang the thing against the side of the pond to get it started, kind of what my wife does to me.
Anyway I found that the stainles steel shaft was so worn that it was a tapir. It thinned to a point and the end of the shaft was stuck in the egg shaped hole in the end of the powerhead housing.
Simple repair. I just took a common rubber washer used for repairing faucets, these come in many sizes. I got one that fit tightly in the hole for the armature and I used hot melt glue to affix a "new" shaft (from another dead powerhead) into the center of the washer. Glue gun "glue" is not really glue, but melted plastic. It makes a lousy glue but it is great to fill spaces and it is non toxic.
I pushed the washer with new shaft into the housing and I had to grind off a little of the armature and a little of the other end cap to fit the new shaft with the washer.
Now the thing works like new and the entire repair was 5 cents.
I don't like throwing things out, because I love fixing things