According to what's on Deltanet, the email to Pilot Selection should trigger a review within 30 days, and this jives with my experience. I submitted my app last year, received a fix-it email about a week later (incomplete work history), then a buddy at Delta sent the email to Pilot Selection about a week after that, and I received an interview invite shortly thereafter.

Overall moral to the story, therefore, is to make sure your app is absolutely suitcased prior to having a Delta friend fire the email to Pilot Selection! Especially since it also states on Deltanet that you're limited to firing off the email trigger once per year per candidate.