I'm sure some may disagree but it seems to me that about only advantage of rear air bags is if you're towing something it stays level.
Everything else I read about leads me to conclusion that OEM coil springs setup is superior to air bags.
Also, if you shop around it's actually relatively inexpensive to switch to conventional setup.
Case in point: For under $1200 I got parts listed bellow and I'm about to tackle it this weekend (all parts are either OEM, Bilstein, Vaico or other reputable brands)

Rear:

2 x Bilstein Performance (not sport) yellow shock
2 X OEM BMW rear coil spring
2 x OEM BMW shock boot
2 x OEM BMW upper spring pad
2 x OEM BMW lower spring pad
2 x Vaico shock mount
2 x Febi additional shock absorber (hard foam insert)
6 x OEM BMW shock mount nut


Front (reuse OEM coil springs):

2 x Bilstein Performance (not sport) yellow strut with built in boot
2 x OEM BMW upper spring pad with built in bearing
2 x OEM BMW lower spring pad
2 x Lemforder strut mount
6 x strut mount nut


I consider Bilstein Performance (formerly called HD) to be perfect replacement for my X5. Some claim they're to harsh but I believe it's matter of personal choice. I have them on both E39 and my wife and daughter don't consider it harsh either.
P.A soft that I have can easily delete suspension warning light after removing rear air bags.

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2010 BMW M6 * Black Saphire Metallic * Full Black Merino Leather
2019 BMW X3 M40i * Alpine White * Mocha Leather