Another question:

What is the expected life of the rear brake pads? I still have my original brake shoes in the rear from when I bought my bike 2 years ago. I have travelled around 20,000km (around 12,500 miles) and am wondering when I should replace them.

You most likely will never wear them out - but they can get dirty, and contaminated with rust.  If your bike sits outside and gets wet, or you don't take it out for a ride to dry the brakes after washing the bike - rust can form on the steel/iron brake drum and get embedded into the brake shoes.  This can make the brakes grabby and squeaky.

It doesn't hurt to clean the dust out of the brake system, and use some sandpaper to clean the surface of the brake shoes occasionally.  At a minimum that can be done when you get a new rear tire.  (And taking the brake backing plate apart and cleaning and greasing the operating shaft should be done more than once in a lifetime).

Thanks for the info.