Is unlocking my iPhone using the UnlockMySIM card permanent?

The UnlockMySIM (UMS) card will unlock your iPhone permanently as long as you do not restore the device to factory settings. 

You may also update from iOS 11.2 to 12.1 Beta 5 without having to insert the ICCID again.

If your iPhone relocks for any reason, simply follow the UMS instructions we sent you to unlock the device again.

We cannot guarantee that the UMS will work if your iPhone has been jailbroken. If it has, we recommend restoring the device to factory settings before following the instructions to set up the card.

We strongly advise against jailbreaking your iPhone for security reasons.