The thing is that recognizing something as premature optimization isn't the same as disregarding it. Developers that spend all of their resources optimizing for minimal battery life impact or other minutia are just as bad as developers who refuse to publish their SaaS app until they're confident that the infrastructure will support one million concurrent users.

Release early, release often. If users love your app after release, focus on fixing the littler things like battery usage. If users hate it, try to fix the things that make them hate it, and then focus on the battery life.

Caveat: As in all optimization discussions, there are reasonable minimum thresholds for acceptability even in the "unoptimized" state. Desktop software can't take thirty minutes to boot no matter what stage of life it's in, and mobile software can't kill your battery in an hour or crash the nearby cellular network at any point either.

Don't make your software egregiously bad; just make it good enough.