Is it binding upon one who covenanted with Allah to fast specific days upon doing something, and who has done that thing, and the number of days reached 45 days, to fast or to pay a financial expiation?

There are two scenarios for this issue: The first is if he says, "Every time I do such and such, I owe a day of fasting," or if he intends for the vow to be repeated with the repetition of the action. In this case, he must fast for the number of days corresponding to the repetition of the action, as long as he is able. If he is unable, then he owes an expiation for breaking an oath (kaffarat yameen). The second is if he says, "If I do such and such, I owe a day of fasting," and he does not intend for the vow to be repeated with the repetition of the action. In this case, he must fast for only one day.