What can I expect the life expectancy, by time and mileage, to be for the 2004 DTS mufflers?

The reason I'm asking is that I noticed some black drip spots the size of a softball on the garage floor, in Birmingham, AL, under the front end of the mufflers this past week. The car has over 116,000 miles now; but, runs and sounds fine still. The black spots got my attention though. Don't know what caused them as it'd been about 2-3 days since a run through a car wash, and had been driven dry a couple of hundred miles on an 85 degree day.

 

it sorta depends how the cars is driven. for example in the city on short trips the mufflers wear out faster since water builds up in the exhaust and rusts the mufflers out. Also the type of weather elements such as if your in snowy climates and road salt is used it can rust out anything under the car thats not protected such as the exhaust. i have a 98 seville with 100k and still has original mufflers and the car lived most of its life in southern california and arizona. Now its in nebraska and they still look good but i wash my car alot too. So it just really depends how the car is cared for.