Spin the water pump pulley when you have the belt off. If it's wobbly or has rough bearings, replace it, otherwise let it ride. My water pump is original at 32 years old and >180K miles, it's finally in need of replacing and I suspect more due to age than miles.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]