What's with the WARNING on greases that says: "Do not mix greases of different type. Use a solvent to remove and clean out ALL TRACES of incompatible greases before repacking." How do you clean out all traces without disassembling! Who's got the time to "clean out ALL TRACES"? Is one stuck using the same grease forever? What if you bought your equipment used, how do you know what was done before? Any thoughts from the experienced?