Mine lasted for 2 years and were still firm when I sold the car 2 weeks ago. The driver's seat in particular did not lean to the left at all, as is common on these cars.

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280