The thing is..... hydraulic filtration goes down to 10 microns "at best".
Oil film thickness can be 1/2 micron when a pump is "working hard".
So particles between ----> ~2 and 10 microns are flowing freely, getting mashed between your precision surfaces.
So there's a lot of steel dust that you cannot filter out, you just live with it.
There is a "normal component lifetime" associated with "normal levels of lubricant contamination".
If you can reduce contamination, longer component lifetime can be expected.
One way is to replace the hydraulic oil at shorter intervals.
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It's cool when magnets catch and hold larger particles.
But on on very tiny particles, magnetic attraction is very weak. Like the fine dust on a magnet, it's just "barely held" by a magnet.
The magnets don't draw fine steel dust out of the oil. But they can "hold it" if it drops down onto the magnet by gravity (when the oil is "still").
That's why you'd want lots of magnets spread around rather than just one drainplug.
You want to catch and hold any very-hard steel wear-particles for sure.
Brass & aluminum can be considered a "cushion" - they are the best kind of dust to have

.
Stone is bad though. Water is bad.
The concept of catching & holding oil contaminants "out of the flow" in a non-moving area on the bottom of the reservoir seems reasonable to get longer life from valve bodies and pumps.
Then the bulk of the hours, the machine is operating with the upper stratification (the more purified) oil.
The gravity method seems "real easy" too (good for the lazy person !!)