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Paul Shaffer has been David Letterman's sidekick since 1982 . . . and he's  under contract for two more years.  But he's thinking about retiring once  that deal is up . . . even if "The Late  Show"continues.

He says, quote, "We've been on 30 years so now we've got another two years .  . . [and] I'm going to be certainly ready to lie down after that, take a  nap."

But he hasn't made a final decision yet.  He adds, quote, "Life is nutty  . . . anything can happen.  I've been so lucky and blessed to be working  this long in show business.  And whatever happens now is just gravy to  me."

Paul reportedly makes $5 million a year on "The Late Show".

Next year, Letterman will surpass Johnny Carson and become the longest  tenured late-night talk show host.  His current contract runs through  2014.  There's no indication that he plans to stop then.  Letterman is  65.  Paul turns 63 next month.