I think mileage and time both should be considered. I have replaced all the hoses on my 95 E320,,, 133K. While the hoses on my 95 SL with 62K still seem to be like new.

__________________
95 SL500 Smoke Silver, Parchment 64K
07 E350 4matic Station Wagon White 34K
02 E320 4Matic Silver/grey 80K
05 F150 Silver 44K