Just serviced my wife's i3 REx at 50k miles. Pollen filter, oil and filter change and the dreaded front suspension dust gaiters. I think they were done under warranty 2 years ago. That's poor to be changing them already. The parts are a few pounds, but main BMW dealer will take your kidney as payment.
One thing to be aware of, and probably not for our US members unless you live in the mid West or the East coast, is the top suspension bearing can fail if exposed to road salt. The bottom alloy bearing race had completely sheared, as the build up of salt and corrosion on the alloy mount had literally expanded to break it.
The job is straight forward, if you release the bottom ARB mount and the top mount (13mm bolts) then lean the suspension strut out from the car. You'll need 18mm drop ring spanner for the tub damper, star drives, suspension coil spring compressors, (Draper or Laser) 2 jacks. Get a axles stand in there too for safety. Use a strap on the strut to the chassis to avoid damaging brake lines or ABS sensor wiring.
This is a great how to video. https://m.youtube.com/watch?v=N4uJneROckI