6000rpm can put a bit of strain on belts, especially if over tightened or if the accessories are not moving freely.

We've never had a belt issue on any of our cars..... my 300SD belts squeal a bit when first started as they are worn/too loose for the alternator load....they've got 65k on them and are being replaced soon.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)