i believe that MB recommends flushing/relacing brake fluid every 24 months. do i think it is necessary: no. do i think its a great idea: YES!!!
if your fluid is older than 2 years, i would recommend having the system flushed and filled with fresh to spec fluid. cheap insurance that could avoid a BIG headache.
i know i could push my car if necessary, but id hate to TRY to stop it flintstone style!
its also a good time to have the entire braking system inspected.