I wonder how necessary the sleeve is? I suspect its only there to keep the dissimilar metals at the joint dry. For those who are worried this side of the fix, it might be an option to slide the sleeve down to have the joint visible, preventing the corrosion by regular cleaning and drying which will also make for frequent safety inspection.
It is just a cosmetic thing, it has no other function as far as I can see - it covers the beginnings of rust in the cracked chrome plating caused by the big crimp dents. Always worth pushing them down and drying off underneath after washing the bike, it keeps the rust at bay.
