M104 is pretty bullet proof. The thing that will cause pre-mature problems is overheating. Make sure cooling system is maintained 100%. This means routine coolant flushes(MBZ coolant only), replacement of all cooling system hoses, new thermo if engine has over 100K miles, test for proper operation of auxiliary fan, assure that serpentine belt is in good shape. These are simple things to make sure your motor runs cool. Excessive heat and/or overheating due to a bad hose or failed fan switch can cause cylinder head warpage and/or cracks, and failed headgaskets. Remember this engine has a lot of light weight alloy components that need to be maintained properly.