There might be some parts for Sears water softeners that you only could get from Sears, but most of the wear parts are available from other sources for a lot less money. I read once that Sears manufactures almost nothing, but has other companies build most of their products.
My Sears Kenmore water softener is about 16 years old. My well water is fairly hard, but the main problem with it is the iron. The softener deals with the iron problem pretty well.
Unfortunately the iron particles must be a bit abrasive, as the softener has needed a new seal for the rotor to slide across for awhile. I took the valve body apart and it was apparent that the iron in the not yet treated water had coated the seal and made the rotor stick in one position. I cleaned off the iron deposit and it worked again, but I wanted to try a new seal.
I looked up my water softener on the Sears parts site, and was SHOCKED at how much they wanted for the seal, which is just a little bit of rubbery material and some harder plastic. So I did some hunting on the internet, and found parts that work just fine for less than half of what Sears wanted for their replacement parts.
I originally bought the Sears water softener because the whole unit was available at what I thought was a reasonable price, and it appeared that most any homeowner with a little bit of plumbing skill could install the Sears unit successfully. I cannot fault the performance of the Sears Kenmore softener. And the few problems I have had with it have been things I could diagnose and fix myself. Service calls have become ridiculously expensive, in my opinion.
But I DO fault Sears prices for replacement parts. They are way higher than what I found I had to pay for the same part (probably made by the same manufacturer). I don"t like feeling like I have been ripped off...and think Sears parts are way higher than they should be.
Would I buy another Sears water softener? Probably, but I would get the least complicated one I could find.