From research I did air gets in microscope pores in seals, hoses & m/c cover. Had stainless steel brakes rebuild a pair of calipers off a super bee I had. Tag on calipers said not to use silicone brake fluid.
I was in a very similar circumstance back in 02 I bought a set of wilwood calipers and their instructions said not to use Dot 5. They even had a big red tag hanging off of each caliper that said not to use 5. I did anyway. Now 20 years later zero problems with those calipers. And Wilwood changed their mind and now they sell their own dot 5 fluid.
The thing is dot 3 and Dot 4 attract moisture. It gets sucked in past the seals in any place else it can because the fluid draws it towards it.
Dot 5 does not attract moisture. It's neutral. There's no attraction, so moisture doesn't go into it. I never flush mine. And I live in a very moist climate, plus freeze and thaw, frost, and condensation. I've never had a cylinder corrode or leak even after 40 years with the same dot 5 fluid in it.
