Do you know that the useful life of a maintained pumping units is 50+ years? Quality used units require the same maintenance as a new units. Repairs on used units will consist of the same items that need to be repaired on new ones. Crank pins, saddle bearings and tail bearings will always require grease and at some point, be required to be replaced. A pumping unit operated within API loading limits should see no reduction in useful life if purchased new or used.