Not sure if this is an E87 or F21 but discs can't be reused when over 1.6mm of wear. You can change them yourself and don't even need a scanner for the reset

 

Sorry should have mentioned its a 2019 car.

Im trying to find the actual thickness of disk that's acceptable so I can measure it. I don't know the new thickness to start with. Some have min thickness stamped on the outside, just dont know with beemers.

 

Wonder if they have a time period where they expect to change - but it should be easy enough to see if they have run down to the point of actually needing changing.
Their expectation of 'soon' might be on general usage too.
Side thought - if they're low then a MOT might comment on them.....

Ages ago I had a Citroen Bx that seemed to need new discs every year, but that was more that they were of poor quality.

Ahh just seen update - 15k a year is above what used to be considered 'normal' - 12k, but with recent covid stuff all that is probably way out of normal now...

 

Still not clear if it's an F40 or F21

If it's the first pic, it's got 280x10 discs on the rear. That means you can just swap pads if your discs are thicker than 8.4mm.
If it's the second pic (F21), it's going to have 290x11 discs, so 9.4mm minimum thickness when installing pads.
Since this sounds like the first brake pad change, you can probably keep the old discs on.
What you describe as the disc service being shown sounds like the brake pad warning. What is the remaining mileage it's estimasting?

 

Ah sorry, forgot there were two around in 19! Its the second one. It says there's brake pad service in 1300 miles.

 

The minimum disc thickness is almost always stamped on the horizontal side of the disc hub. Usually says something like Min Th xx.xx MM.

30k is not at all impressive for rear pads/discs unless they've been repeatedly allowed to rust which accelerates wear.

My 635d gave 85k off the rears and 100k off the front. Even my old X5 is on it's original set at 60k. The 'remaining wear' on the idrive is comically inaccurate so take with a pinch of salt - it's a bit like the old MS Windows time estimations, 3 mins, 2 mins, 8 days, 47 years, 3 seconds, 4 minutes, 2 hours, done!

Also worth noting is that BMW will flag stuff as needing to be done that is deemed likely to require action before the next scheduled service. So if they think they won't last the next 20k they start mithering you about them at the current service even if they might have another 10-15k in them.

 

Is the cruise control used a lot? I heard that on some cars the rear brakes are automatically activated to help maintain the set speed on downhill stretches of road.

 

Thanks all for the advice, thats really helpful. The cruise is very rarely used.
I can check the disk thickness and at least make sure that they need changing or not whoever does it.
Does anyone have any input as to whether me changing pads and/or disks would cause warranty issues especially as its on a PCP?