The answer all depends upon what type of hair you have: thick or thin, tight curls or straight wisps, lots of it or not so much at all.
Some people are everyday hair washers by choice, other people like athletes need to wash their hair daily to get rid of sweat. Alternatively, if you are an every-other or just a couple-of-times-per-week washer that works too, as long as your scalp doesn’t get too oily.
The scalp actually gets used to your routine, so it’s when you go an extra day without washing that your scalp tends to put out lots of oil. This can be especially true for everyday hair washers, who get super greasy hair when they skip a day because the scalp is trying to compensate in between washes. Keep in mind that if you want to change-up your hair washing frequency, it might take a couple of weeks for your scalp to get used to a new routine.