If a person performed tayammum for janabah due to an excuse, then he became حدث (minor ritual impurity), and he is able to perform wudu but not ghusl, is it sufficient for him to perform wudu, or must he repeat tayammum every time he becomes حدث or wishes to pray?

A person in a state of major ritual impurity (junub) who is unable to perform ghusl (ritual bath) should perform tayammum (dry ablution), even if they are able to perform wudu (minor ablution). Tayammum does not completely remove the state of major ritual impurity. Therefore, if the junub person finds water, they revert to being in a state of major ritual impurity. This is the view of the majority of scholars.