Add job offer later

I recently submitted my EE profile and my score is ~400 (with IELTS overall score 8). I see that cutoff for most of the months in past is around 450+. If my application doesn’t get picked in their allocated time lot, how long would they still keep it in system? The reason I ask is I am working on getting an employment letter while we speak and if I manage to get one, can I add that to my existing application or do I have to reapply?

EE profile stays in pool for one year. You can delete and submit new profile whenever you want before that. There’s also an option to modify the profile.