...sounds like you have the current MB floor mat
I've found that Lloyd manufactures a handsome super premium model floor mat that is significantly heavier vs. the current MB floor mat, fit is perfect- front & rear, has rubber backing (no slip, no H20 problems), also comes with extra metal hook/clips for even more no slipping insurance, color is black & matches interior ('94 E500), also has heed pad for extra cushioning, no MB insignia's on mine- but I understand they can be custom applied ...the Lloyd mats appear to be made to last as long as the car - pricing was similar vs. MB mats
I have current MB floor mat's in my '94 E320 Coupe and they have worn well for the past 4 years, but appear to be made to last about 5 years with daily use.
fyi- I've also got a set of MB OE "all-weather" mats that I use between W124's as needed, and they appear to be made of military rubber to catch all H20 and dirt.... they are very inexpensive (less than $80 retail for the W124 /4 piece at any MB dealer and will definitely last longer than a W124)
hope this helps