submission to the emperor as Italian states and is it permanent?

[Strifeboy]

I don't see a date on it and worried that it's their forever.

[Surimi]

Do you mean the shadow kingdom event?

Basically, submission to the Emperor will keep you in the HRE, with all the benefits and drawbacks thereof (generally, until you're ready to form the kingdom of italy, the benefits outweigh the drawbacks). It is "permanent" in the sense that the event will only fire once, but it is not difficult for any country to leave the HRE (far easier, in fact, than getting in).

The main downside is that submitting to the emperor will lower your prestige by a big chunk, while leaving the empire will raise it. Since prestige will normalize over time, this is generally not a big problem and should not deter you from remaining in the HRE if you feel you still need protection.

[Adrazar]

You can totally get rid of the 'submission to the Emperor' modifier while staying in the HRE. Not going to tell you how... but you do it in a very logical way ;)

[Quicksilver]

Becoming emperor of HRE, culture converting to a different group or leaving HRE will remove it.