In an evolutionary context, a limited lifespan means that a fixed set of computational resources can be used to explore more candidates.
also true! We've added it to the paper (linking your comment). It's extremely important because the 5k lifespan takes literally up to five times as long as the 1k lifespan. Sent you an email, let me know if you'd like a formal acknowledgment in the paper.
Shortening lifespans paradoxically resulted in benchmark saturation (100% survival) - and as the other comment here points out, it takes much less computation, too!