19 years plus the 10 years in the early 2000s where Universal built nothing.
From Wikipedia...
UNIVERSAL STUDIOS FLORIDA:
April 4, 2000: Men in Black: Alien Attack opens in the World Expo area, on the former site of The Swamp Thing Set.
Summer 2001: Animal Planet Live opens, replacing Animal Actors Stage.
December 2002: Macy's Holiday Parade debuts at the park.
April 11, 2003: Jimmy Neutron's Nicktoon Blast opens, replacing The Funtastic World of Hanna-Barbera.
June 12, 2003: Shrek 4-D opens with Donkey's Photo Finish, replacing Alfred Hitchcock: The Art of Making Movies and Stage 54 respectively.
May 25, 2004: Revenge of the Mummy: The Ride opens, replacing Kongfrontation.
May 2005: Fear Factor Live opens, replacing The Wild Wild Wild West Stunt Show.
Spring 2006: Delancey Street Preview Center opens in the New York area.
July 4, 2006: Universal 360: A Cinesphere Spectacular opens, replacing Dynamite Nights Stunt Spectacular.
Fall 2006: Animal Planet Live is closed, and replaced by Animal Actors on Location.
June 6, 2007: Blue Man Group Sharp Aquos Theatre opens in CityWalk, replacing Nickelodeon Studios.
January 17, 2008: Disaster!: A Major Motion Picture Ride...Starring You! opens, replacing Earthquake: The Big One
May 15, 2008: The Simpsons Ride opens, replacing Back to the Future: The Ride.
February 21, 2009: The Universal Music Plaza Stage opens, replacing The Boneyard.
August 19, 2009: Hollywood Rip Ride Rockit opens.
ISLANDS OF ADVENTURE:
2000, May & June 29: Flying Unicorn and Storm Force Accelatron debut in the park's The Lost Continent and Marvel Super Hero Island areas, respectively.
2000, December: The annual GrinchMas event begins in the park's Seuss Landing area.
2002 Matt Hoffman's Freakin Crazy Stunt Show
2006, June: Sylvester McMonkey McBean's Very Unusual Driving Machines is rebuilt into a new concept, and officially opened as The High in the Sky Seuss Trolley Train Ride.
2009, October: Oh, The Stories You'll Hear! opens in the park's Seuss Landing area.
2010, March: Mat Hoffman's Aggro Circus debuts in the park's Toon Lagoon amphitheatre, the theater's first show since Mat Hoffman's Freakin Crazy Stunt Show in 2002.
2010, June 18: The seventh island, The Wizarding World of Harry Potter, is officially opened with a grand opening ceremony. The area is Islands of Adventure's biggest investment since the park's opening.
2010, December 13: After five years, Triceratops Discovery Trail is finally reopened to the public for a limited time, speculated to further remain seasonal during peak season.
...so, although lots of attractions replaced others (so the numbers of attractions didn't grow), Universal Studios Florida opened
something every year between 2000 and 2009. Islands of Adventure got quiet after a while (something opening in 2004 would have helped bridge the gap between 2002 and 2006), but they did open 14+ attractions in 1999.