How many suits do you own? If you wear them on shabbos only, the right answer is probably three or four.
You want to be able to get through a three day yom tov without going into reruns, and you want to be able to wear two per weekend, without wearing the same suits two weeks in a row. Also, depending on your climate, you may need a flannel or a summer suit - though I can't recall ever seeing a Jewish guy in seersucker or linen in shul.
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