I must admit I was taken aback when I first worked on my TT brakes. My first thought was "what a Rube Goldberg concoction." An electro-magnet riding against the brake drum pulling on the brake shoe lever. Still I had to admit I had nothing better to offer.
My TT was 3 years old and lightly used when I bought it. 2 1/2 years and 21,000 miles later I can tell you that the magnets are deeply scored and very dirty. I have had to replace two that had worn through to the copper.
When I had the bearings packed I was told they "looked" okay. Now I look for myself.
I do not know that there is much that can be gone except to periodically replace the magnets and drums and to adjust them as needed.
I was curious how often others service their TT brakes.