So, it has been announced that Ariel Castro has been sentenced to life plus 1,000 years for kidnapping 3 women and holding them captive for almost a decade.  Keeping him for life is a great idea.  But what's with the additional thousand years?

If he dies, is he expected to come back and possibly be free?  Is this time in addition to life in place because of people who "died" and are revived within a few minutes? Is the justice system afraid that if a person comes back, they may be free on a technicality?  I've never understood why a sentence of "life plus" is necessary.  Do you?