Vader zeta ability

Hi everyone I will soon get my first Zeta and I was wondering to give that to Vader.

Im just not sure of how this ability will work!
When the dot will be expire and when not?
Some example:

1 dot expire from itself after 2/3 turn.
2 a cleaner like Rex use his special for take out all the dot and gain tenacy up. What's happen in this scenario?
3 the dot expire after a culling blade from my Vader or the execution of boba. They come back?

I can't think other example but for sure there will be.
Thank you everyone for the answer!