In 2300ad, Lavos' life-cycle is in its reproduction phase, drawing on the genetic material and magic of the earth to create stronger, fitter Lavos spawns. Once these spawns mature, I think they would consume the flesh & energy of Lavos, killing him in the process, and then depart for other planets. Lavos would willingly die this way, as his own life would be complete, and it would maximize his offspring's chance to survive, thrive, and continue the cycle. Likewise, if any of his spawn came out dysfunctional or otherwise unfit, it would be killed & consumed by Lavos. All this is in accordance with Darwinism, which applies even to him, and there are species irl who do as I described.