2 years ago I replaced my calipers with Raybestos OPTI-CAL line of brand-new non-remanufactured calipers.
A quick inspection reveals that the guide pins have already been torn and the caliper piston dust boot is cracked and torn as well--------2 years!!! The OEMs that it replaced after 12 years of service were still good (the rubber boots that is.)
So, this unit still works but I’m going to pre-emptively replace it with a CardOne remanufactured unit (wearing the WEAREVER brand) from Advance Auto.
Question is: should I generously apply Sil-Glyde to it (even on the outside.)
YES, it will be covered in brake dust but that won’t impair its functionality
I’ve never encountered a rubber-parts problem on my brake calipers before, but I have on CV boots. I finally figured out that the deterioration of the CV boots was caused by inadvertently getting oil, solvents, and WD 40 on them. Since then I’ve adopted the practice of cleaning the boots and their folds with mild soap and warm water using a paint brush followed by a water rinse at every oil and filter change, and never had much of a problem with boot deterioration since. The inner CV boots on my 27 year old Corolla are original to the car. I expect you’d get best results just by keeping the rubber parts on your calipers clean, and otherwise applying nothing.
Sil glyde or pure silicone grease is the generally preferred stuff for the rubber parts in your brake caliper components. However if the boots on your slide pins are torn I would probably go ahead and get those replaced.