When a phoenix molts from one life to the next, it does so in a dramatic fashion by making a funeral pyre.
An observer would assume that this is painful but quick, however time stops while the phoenix is engulfed. Seconds become hours, days, weeks, maybe years. This cleansing via fire does not come without punishment by the same method. Such are the dry parallels of the phoenix existence. Each glimmer of hope corresponds to long stretches of agony.
One hopes that over time the glimmers get longer and the agonies get shorter until finally there is only hope and the phoenix can emerge into a new life.