100,000 mile tune up??

What is your question?

Does some of the cadalac engines have aluminum heads on older models back in 1990? Is it safe to drive a car say 15 to 20 yrs and get tuned up at or on the 100,000th mile? LOOKS LIKE ONE MAY HAVE SOME PLUGS SIEZED UP IN THE HEADS??? This is less than 10,000 miles a yr! Is this a safe serviceing option or a sales gimmick??