Afternoon all.
I came across Never-Seez in the early eighties when us dispatch riders were trying to prevent our brakes seizing up. It differs considerably from normal copperslip, as it's somewhat thicker in consistency, & is a right old cocktail of things including Aluminium & Copper, & it has a melting point around 1100 degrees centigrade.
I certainly wouldn't recommend using ordinary copperslip on caliper pistons, as most cheaper varieties are much more oily, & there is the possibility of the seals swelling if an excess of oil comes into contact with them.
I have found that applying Never-seez to the pistons on top of the rubber lube prevents the rubber lube from being washed away, & also provides another layer of protection when it comes to preventing water entering the caliper & getting behind the seals.
My mates XJ900 dispatch bike retired after 8 years & 215k miles. I had regularly cleaned & lubed the calipers 'my way'. It had never needed a caliper overhaul & the wheels still spun freely. There have also been countless others that I have serviced over many years...I rest my case M'lud!
Cheers.