Once you do your career will be dead. Non US airlines don't like instructors
Utter tosh, my friend.
I am struggling very much to find experienced instructors because (in the last year alone) I have had three of my senior ones 'stolen' by the airlines. To worsen my situation I'm sitting here with a 50+ year old instructor about to head off on his first airline gig.
Even applications for 'newbie' positions are drying up. Famine or feast.