No, it isn't a must do. I replaced my drums and shoes quit a few years ago and have not yet needed to adjust the rears in 10,000 miles. I have checked them when the car was up on a hoist and the rears still make a scraping noise so they are adjusted just fine. I have disc brakes on the front so they do most of the stopping.
I have the hardware to add the self adjusters but I haven't had to service the back brakes so I will not add the adjusters until that time.
As to how the adjusters work, when you apply the brakes going forward, the shoes and the hardware take a set. If you have worked on your brakes you know the shoes can be move around a little. So, when you apply the brakes going backwards, the shoes actually move and take a set that way. This causes the adjuster to click the star wheel a small amount because the adjuster is mounted on the shoes and the star wheel is mounted on the backing plate.
If you haven't worked on brakes before, this explanation is probably not going to make any sense.:sign0020:
A forum community dedicated to 1955, 1956, and 1957 Chevy owners and enthusiasts. Come join the discussion about restoration, engine swaps, reviews, performance, modifications, classifieds, troubleshooting, maintenance, and more! Open to all models including Belair, 210, 150, Sedans, and Nomads.