the in game description of the LCN says that as long as you wear it, you'll be a leithan. does the removal of the necklace revert you back to what you were before? if not, will it? the description seems to imply it.
I don't believe the effects would be reversible otherwise by just simply taking the necklace off. Any TF effects that took place while wearing the necklace would be permanent until you otherwise transform them from something else.
The wording is poor. So long as you wear the necklace roughly every 3-4 hours you get a transformation. Take the necklace off, you stop transforming. Keep the necklace on and eventually you become a leithan. Take any other transformatives while wearing the necklace eventually you'll become leithan again. With the necklace off you are free to go about tranforming yourself however you see fit again.