Well pumps last 8 to 12 years on average. Replacement cost $3 to 5k.
Well life span is really dependent on water chemistry, soil type, formation that is producing the water main issues are casing failure due to rusting or corroding or aquifer simply plugging off or fouling. First indicator you may have failing well casing is increase in nitrate levels, positive coliform bacteria, or e-coli in the well samples. First indication of aquifer plugging is reduced pumping capacity, or reduction is specific capacity (gallons per minute/foot of water level draw down). Wisconsin is very varied geology across the state so I would expect life of wells to vary with location of wells and quality of water.
The other issue is wells constructed in the 1970’s and earlier had very minimal surface seals which make the wells more susceptible to contamination.
Replacement well locations can be tricky if you dont have the space in the park. This is always my number 1 concern where can you put a new well if needed. Do you have the proper setbacks from septic systems, tanks, drainfields etc.