Will I need to unlock my phone again?

I recently acquired a used Windows phone from a private party and I used the AT&T unlock utility web page. I successfully unlocked my phone without further incident. My next concern is regarding the phone's unlocked status. Will the software ever trigger the locked mode again, i.e., during a factory reset exchanging to another party or reboot submission for maintenance.

If so what's the process? Another unlock request to AT&T or do I use the same unlock code that I used today? Thank you. I appreciate any feedback.