Imagine a Hindu and a Christian, both of whom have absolute faith (i.e., they firmly believe and harbor no doubts whatsoever) that their religion, their theology, their deity/deities are true and real. Now given the fact that the claims made by the two religions are in conflict with one another, they cannot be simultaneously true. If the Christian claims are true then those of Hinduism are false, and vice versa. So at the very least we know something for certain--that at most only one of them can be right. Therefore, the probability that at least one of them is wrong is 100%. This we are sure of. (Note that I have emphasized "at most" and "at least" since it is quite possible that both believers are wrong.)
Focus now on the fact that our above devotees both have what other supernaturalists would envy and do try to achieve--unremitting and absolute faith. Notice how the fact that they both have "maximum" faith has nothing to do with the undebatable fact that at least one of them is wrong. Hence, in this simple exercise we clearly see that belief, however fervent it may be, has no bearing on whether what is believed in is true or false.
Given this, it is quite puzzling why there are supers who urge their fellow believers to have faith or to strengthen their faith. As we have seen belief is independent of the veracity of what one believes in. As I see it the call to intensify or consolidate one's belief has nothing to do about the truth of the claims/beliefs. Rather it is about ingraining a particular worldview, about the psychological goal of making one take for granted this worldview and its beliefs, and about the social objective of becoming a model for other (potential) believers to emulate.