Most times it is the lever (lever parking brake adjuster left and right) that wears first or rusts before the star wheels wear out. If you can turn the star wheels by hand ( and they aren't frozen on the threads), the (adjuster) lever isn't worn, rusted or just plan rotting apart, it should self adjust if it is put together correctly.
Where a lot of people go wrong putting them together is the cable guide, about the middle of the adjuster cable. It has to sit flat against the shoe and is sometimes hard to get together and held in place while you are installing the spring (one of those jobs that takes three hands or a little luck to get right the first time). The bevel on the bottom of the cable guide pops out of the hole while you are trying to install the spring end that holds it in place. It can be hard to see, but the end effect is it leaves about 3/16" of play in the cable. If the cable guide isn't sitting perfectly flat on the shoe it is not put together correctly.
If your star adjuster isn't frozen, your lever isn't worn out and the cable guide is installed correctly, your brakes will likely self adjust.
You can apply your parking brake just until you feel a little resistance while backing up. Then back up at a moderate speed, say 3-5 MPH, then apply the brakes sharply, but don't lock them up. Repeat a few times, then notice how your brakes just feel tighter.
The self adjusters adjust in reverse, if you don't back up often, or are really light on the brakes when you do back up, they may not self adjust.
I use motorcycle chain lube on my star wheel (adjuster) threads, a lite coat of lithium grease or copper paste also works. A tiny dab of Lithium grease (or copper paste) behind the adjuster cable guide, some lubrication on the star wheel adjuster threads and have few if any issues with my self adjusters. I swap out the adjuster levers every 5-7 years, a few bucks appeace. I've never had to swap out a star wheel (or adjuster assembly).
The only other issue I can think of is, if you disassembled both brakes at once and got the star wheels mixed up. They are left and rights, one has reverse threads (I forget which is which). I never do both sides at once anymore, I only made that mistake once.
The self adjuster setup has been around forever and is proven technology that works. Especially when you consider that the brakes get, hot, dirty and are constantly exposed to the elements, the system holds up reasonably well. It just needs a little cleaning, lubrication and service every now and then.