I picked up a used RCM for about $45 12 to 14 years ago, prices have gone up since. I soldered the weak spots and put it in my trunk just in case it was needed. I had a NA at the time.
A couple of years ago I had cause to buy a used BCM, I did not need it as it turned out so it went on the shelf.
One day I thought I should make sure they worked so I exchanged them for the originals, they both worked fine so I left them in and put the originals in the trunk and on the shelf respectively. My point being that you make sure that the spare RCM is working properly.
In the trunk I have the RCM, and new Crank and Camshaft PS’s as you never know when you’ll need them.
As far as I know the CPS’s are original, at least they have been in the car for the nearly eleven years that I have had the car. I see no point in replacing these items while they are still working.