Must a person offer expiation for each time they swore by divorce regarding the same matter with different people, or is that considered one oath?

If a man swears multiple oaths by divorce not to do something, and then does it, he is bound by a single divorce according to the majority of scholars. If this divorce is the first or second, he may take his wife back before her 'iddah (waiting period) expires. However, if it is the third divorce, she becomes unlawful for him and is not permissible for him until she marries another man and he divorces her after consummating the marriage.