First of all you need to check which type of hub you have on your bike. Are they cup/cone bearings or is it a sealed bearing ?...If it's a sealed bearing then it doesn't need to be greased...Cup/cone hubs also don't need to be greased unless they have few thousand miles on them and have been ridden hard under extreme weather conditions...500 miles is nothing and there is no need to grease them unless the factory messed up and didn't put enough grease.