Depending on the climate you'll start to see steel (coil and leaf) springs start to rust away by ten years. Meanwhile the Tesla S was introduced in 2012 which puts the majority of the problems in cars younger than your relative's X5.
The previous owner replaced the air bags (springs) on my car so I couldn't say if they actually failed or if he did as part of a refresh when he lowered the car. They're not super expensive, but the aftermarket ones are that much cheaper. Of course the X5 (especially the first generation) is one of the least reliable vehicles BMW's brought to market. It's the electronics and pump that get real pricey, but on the E39 they pretty much never fail.
