My C4 Grand Picasso has rear air suspension. Three years ago, when the car was 3 years old with 33k on the clock, both units failed (left, then right) within the space of 200miles. Now, with the car just past its 6th birthday and with 66k on the clock, I found it this morning on its back haunches again ....it had sunk overnight. It's not a total failure (yet) - 3 years ago, when each suspension unit failed, the car would not get off the bump stops; this time, when I switch on, it pumps itself up and drives as normal - then when I switch off and leave it for a couple of hours, it's down again. So it seems I'm getting an early warning this time.

Is it expected of air suspension units that their lifespan is 3 years / 33k miles? The car is driven on 'normal' roads, i.e. not off-road, so hasn't been subjected to any abuse.