The view associated with Abū Ḥanīfah and several theologians is that the fundamental assent of faith is not subject to increase or decrease: decisive conviction is not simply a quantity varying like mere conjecture.
Someone who definitively affirms the truth brought by the Messenger ﷺ possesses foundational assent. More worship may increase reward, obedience, nearness, and perfection, without thereby adding constituents to the essence of that assent.
This view does not diminish the religious importance of deeds. It distinguishes the definition of faith from the believer's excellence in action.