A series of small cracks doesn't mean the belt needs to be replced. I would ask a dealer what MB specs are. I was told by a Ford dealer mechanic and Ford allows up to 4 cracks ones going through the rib, per 1 inch area.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member