which one is better? using random username password or our own username and password?

i would like to know which one is better to use random or our own username and password?

Random username and password seem to do fine for me

thanks. is it possible to use the site with same username and password for our second submission? 

Use the site with same username and password for second submission? You mean post on the same site twice? If that's what you're talking about you can do that with the scheduled posting options.

thanks for your reply. lets say bookmark submission i am going submit my second URL with the same username and password. is it possible?