Think for a moment about why you’d need to make changes after you submit.
Is it because you catch an error or omission? If that’s your concern, then avoid the issue all together by double- and triple-checking your work before submitting. Have a trusted teacher or counselor take a look too.
Is it because you’re expecting some information to emerge later that you might want to add? If that’s the case, then don’t submit until you have that information. Of course, the main guardrail here is the deadline itself, which you don’t want to miss.
I believe most mistakes happen when the candidate is in a rush. So mitigate that. If you’re a procrastinator, manage the task carefully so that you’re not scrambling. If, on the other hand, you want to be an early bird, know that there’s not necessarily a reward or advantage for submitting early. Especially if being early means you make careless mistakes.
As we say on SAF often, submit the best application you can as early as you can. Emphasis on “best.”