1: The water pump should have some very slight resistance caused by the shaft seal.
2: The revolution of the water pump should be smooth. If it feels rough or "cogging" the bearings are on their way out.
3: Grease isn't the problem, water ingress due to missing caps and heat/age kill the bearing. Everything has a finite life, they seem to last around 100K.
4: Age isn't as important as condition. Hardened rubber or micro-cracking indicate replacement time.
5: When they need it. Seriously. If the hoses aren't swollen, hardened, cracked, or excessively soft, leave them be. Belt replacement is when it starts showing longitudinal lines (indicating it is worn down), or begins having cracks in the ribs.

The life of the parts in question will depend on how the car is driven, whether it is garage-kept or parked outside, the climate it is driven in, how well it is maintained, etc. Hoses can last for decades if they were quality to begin with and the cooling system is maintained.

__________________
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]