Over three years and 4500 mile total of 10 mile daily use of my Brompton in all weathers I have just changed to my third set of standard Brompton brake pad inserts. At this cost I don't consider it work considering alternatives.
http://brilliantbikes.co.uk/brompton...373410026.html
I guess as I live in Cambridge, its pretty flat so I don't do a lot of hard braking.
Regards
Jerry