Everyone hair is different and some people can do it while others need to do it everyday - If you are worried about over shampooing your hair, get a gentle or a baby shampoo that won't be as harsh on your hair.
My hair gets greasy quickly too but I have heard that the more you touch your hair, the more it will "cleanse" itself by producing grease. So to try and prolong less grease avoid touching or messing with your hair
It's not healthy to shampoo your hair every single day, have this in mind. by the way I'm not shampooing everyday because after I wash it I have 2 bad hair days in a row. I wash it once\twice a week. It's wonderful really :)
Different races can go longer but still wash their bodies, black women use shower caps to not mess it up because they don't want to do all the fuss and it dosent get as greasy for awhile. There is a trick I remember when I was in my teens that worked if I didn't have time to wash my hair, I put baby powder in it to absorb the oils and grease and brushed it out to get away with one more day of washing it