[shaggylive]

I switch phone on my 2 lines all the time.. (ok the 2nd line more than the 1st...)
I only have insurance on the 1st line, but every time I swap phones on the 2nd the next bill has a little blurb about having until xx date to sign up for TEP.

basically as long as the phone hasn't been flagged for damage/loss/theft, then you can add TEP within 30 days of its activation..

and if TEP is already on the line, it should just stay there.... you may want to double check after 24hrs, to make sure though.