Muffler life??

[robi99]

What's the "normal" life expectancy for a center or rear muffler on a 300E?? I know there are many variables; highway driving, around town driving, climate etc.
My 300E was 8 years old with 43,000 miles when I bought it. It was driven by a little old lady and with the exception of a round trip to Florida every year, she averaged 3,000 miles a year. I replaced the exhaust shortly after buying the car so the mufflers are about 4 1/2 years old with about 70,000 miles on them. The center muffler has a hole. The rear is perfect. Did I get a bum center muffler or what?? Both are OEM.