No, but we can throw one together:

Mervyn Peake's GORMENGHAST series: 66 years (from TITUS GROAN in 1948 to the dubious posthumous TITUS AWAKES, due out next year).

Isaac Asimov's FOUNDATION series: 50 years (from the first FOUNDATION short story in 1942 to the posthumous FORWARD THE FOUNDATION in 1992). Much more if works by other hands are included.

Isaac Asimov's ROBOTS series: 45 years (from the first ROBOTS short story in 1940 to ROBOTS AND EMPIRE in 1985). Again, much more if works by other authors are included.

Anne McCaffrey's PERN series: 45 years (from the first PERN novella in 1967 to DRAGON TIME due in 2012; includes stories written by her son Todd based on her outlines).

Tolkien's central Middle-earth work: 40 years (from THE HOBBIT in 1937 to THE SILMARILLION in 1977).

Terry Brooks's SHANNARA series: 35 years and counting (though divided into lesser sub-series and arcs).

Jack Vance's DYING EARTH series: 34 years.

Larry Niven's RINGWORLD series: 34 years. Note that RINGWORLD is a subset of the KNOWN SPACE series, but this is more of a background setting, not a cohesive single series.

Raymond E. Feist's RIFTWAR series: 31 years (by the time it is completed in 2013, assuming he hits the date).

Jean M. Auel's EARTH'S CHILDREN series: 31 years.

Arthur C. Clarke's ODYSSEY series: 29 years.

David Gerrold's WAR AGAINST THE CHTORR series: 28 years (and counting).

Patrick Tilley's AMTRAK WARS series: 28 years (and counting).

Terry Pratchett's DISCWORLD series: 28 years (and counting), though not a cohesive series with a single narrative like most of these others.

George R.R. Martin's WILD CARDS series: 24 years.

Katherine Kerr's DEVERRY CYCLE: 23 years.

Stephen King's DARK TOWER series: 22 years. Except there's a new one out next year, so 30 years. And of course apparently King's entire output takes place in the same multiverse so arguably a lot more if you want to get pedantic.

Robert Jordan's WHEEL OF TIME series: 22 years (when it finishes next year).

Roger Zelazny's AMBER series: 21 years (25 including short stories).

Arthur C. Clarke's RAMA series: 20 years.

Frank L. Baum's OZ series: 20 years (more including sequels by other haneds etc).

A SONG OF ICE AND FIRE, by contrast, currently clocks in at a comparatively modest 15 years, though the chances of GRRM bringing it in at less than 20 would appear to be almost non-existent even through an optimistic viewpoint.