Question on Article Submission

As we all know Article Submission is a good Marketing process. My question is, at what point should you change the text of the submission to avoid duplicate content? Or indeed do you need to change it,and just keep submitting to as many numbers as you can?

well, i have a load of plr articles, so i pick one, and change the title and the text a tiny bit, then submit to as many as possible

So why change it?

because its a plr article, so somnebody has probably already submitted it so i change it a little so that it gets approved

Do you not write your own? or do you find it easier to buy plr ones?

on my blog,some i write, some are just plr

as for article submission, i submit plr, i dont want my own articles all over for everyone else to get credit for

and i get my plr articles free, i have like 60k of them, about 5k webmaster related