I'm pretty sure the "real" release date is set the first time you go to "finished" state, and in any case, doing a "major update or release" devlog will reset the project's "freshness" value... but it requires moderator approval first (probably to prevent people to make posts like those once per day to inflate their numbers unfairly). So you'd be able to stick with the "early access" project tier, update the page when it's completed, and get the best of both the organic traffic world and the "recently created" page world.