If we go outside of Trek Lit there are some novels that cover centuries or even millenia. For instance, a few months ago I got the e-book of London by Edward Rutherfurd, and that covers four million years ago all the way up through 1997 when it was published.Well, that was its brief -- to explain what the Enterprise was doing during the entire first season. And it's nice to get the occasional story spanning a considerable length of time. When you're not obligated to fit stories between episodes, you have room for that sort of thing. Typhon Pact: Rough Beasts of Empire spanned about a year. Voyager: Full Circle covered a couple of years or more. And a number of the Lost Era books span quite a lot of time. My own TNG: The Buried Age covered close to 9 years. Each volume of the Terok Nor trilogy spans from 8 to 10 years, and The Art of the Impossible spans 18 years.