There are three possible ways the brakes will be activated:
- you press them
- when the battery is essentially totally full and you let off on the accelerator pedal - regen works when there's room in the battery, which is most of the time. The computer does this to try to make the slowing nearly the same whether it is done by regen or can't if the battery is full.
- if the car senses an emergency situation where slowing will help in safety
It's not uncommon for salesmen to not have a clue on the vehicles they sell. It's kind of sad, and says something about their professionalism, but the best defense is a well informed buyer.
I seem to remember that the car will activate disk drying when it senses it is wet out, but you don't really notice that as the pads just start to skim the disks to clear them of water...not try to slow you down. IOW, that should not really cause any wear.
As a result, the pads on the i3 should last a VERY long time unless you charge to a stop and require pressing them and don't maximize regen for slowing purposes. As a result, the disks get a light rust coating, so it actually helps once in awhile to do an emergency stop to help clean them up when it is safe to do so.
2011 535i x-drive GT, 2014 i3 BEV
Soon (hopefully!) A 2021 X5 45e will replace the above