One of the reasons that the discs deteriorate so quickly is that Regen reduces their usage so much that surface rust builds up and this eats the discs away MUCH faster than when being used in the 'traditional' way. Our Twizy has just had an MoT and to make sure I didn't get the same Advisory about the condition of the discs as I had last year, I switched off both Lift Off and Braking Regen for 2 weeks before the test, to clean up the disc surfaces. This really worked and the discs looked really good and more importantly, now worked really well just as pure 'friction' brakes. No Advisories and it sailed through the MoT.
Have now put the Regen back on and of course the power of the brakes is now improved, but I will do a regulary 'maintenance' job just like this, maybe twice a year from now on.
As part of the process I checked the thickness of the pads and after 7,700 miles, I need new pads badly it seems, so I am glad I checked things properly this time....!