“[And he calls it (i.e., fire)] ‘need and satiety.'” (R 65; cp. D S 65; Kahn 119)
Fire has two meanings in Heraclitus. On the one hand, he identifies it with one of the elements, along with water, air, and earth. On the other, he speaks of eternal fire, aether, often interpreted as that from which all elements emerge and to which, at least in the Stoic accounts, it eventually all returns, as the world is destroyed — a process that will repeat.
The eternal fire probably appealed to here can metaphorically be seen as compelled by need to consume, which we might imagine as being satiated through the consumption of all it burns (cp. Kahn, p. 276). In Stoic cosmogony, such satiety might be viewed as indicative of the state in which the world eventually is destroyed, before world-formation begins again. For this, we would read the fragment in connection with Fragment 37 (D 30), which speaks of “fire everlasting, kindled in measures and in measures going out.”
What the Stoics saw an fundamental to cosmogony is also to be seen as fundamental to human life — the state of the soul being captured by change and fluctuations among oppositions. Need is sated, but then again arises, only to compel those who have it to movement and motion, to sate it. Such is the state of human life and cosmic processes.