For the amount of play the machines get, there is no reason to use anything but Vasoline and 3 in 1 Oil or any 10w oil. Vasoline will never harden. White lithium grease especially and and other greases will dry out and harden over time if the machine is not played.
I have used Vaseline for many years, on most Trade Stimulators. Both clear & creamy. But for the hard play that Slot Machines usually endure, I have always used Lubraplate on most parts. It does not harden with age. At least in my age range. If it does after I'm gone, I'll never know it!