@oristarA,
It's just used as hyperbole in most cases. That's obviously what FBM was doing.
No one person has a "few lifetimes," but the lifetimes you refer to wouldn't necessarily have to be your own. A "few lifetimes" might be used as a colorful way of saying 200-250 years, given today's average lifespan (whatever it is).
It is "proper English," and is a phrasing you will run across from time to time--but again, generally just in a hyperbolic context.