Electrolux® Corporation/Aerus LLC/TriStar® Enterprises LLC's triple brush machines are definitely in the running.
Electrolux®/Aerus's Lux® Floor Pro (formerly called Floor Beautifier, Floor Pro Epic™, Floor Pro Encore™, and Floor Pro) debuted in 1983 and has been revised since that time under these models:
Model B-9 (1983-84, 2-toned gray; 1984-85, sand sand/jade)
Model 1522 (1985-87 sand/jade; 1988, sand/taupe; 1988-92, lt. sand/navy)
Model B-10 (1987, sand/taupe)
*Model 1732 (1992-93, navy/lt. sand)
*Model 1739 (1993-94, navy/lt. sand)
*Model S105A (1994-95, navy/lt. sand)
*Model S105B (1995-97, gray/coal; 1997-98, oyster/fog)
*Model S105G (1998-00, oyster/fog--75th Anniversary edition)
*Model S105J (2000-02, lt. blue/white)
*Model S105L (2002-05, lt. blue/white)
*Model S105N (2005-07, lt. blue/white)
Model S165A (2007-09, lt. blue/white)
Model S165B (2009-13, white)
Model S165F (2013-present, black/white)
*The models 1732, 1739, and S105s had cord winders.
Its predecessors, the Model B-7 (1959-62 in lt. gray and aqua) and the Model B-8 (1962-83 in aqua, tan, teal, gold, brown, and dk. gray) might also be counted in the longevity for their similar designs.
TriStar's® ProStar™ (current Model S165D, white/gray) is a rebadged Floor Pro. The ProStars™ have likely been around since c. 1998 when TriStar® was acquired by Electrolux® LLC. I'm unfamiliar with its models and color variations.
Electrolux®/Aerus's Lux® Floor Pro (formerly called Floor Beautifier, Floor Pro Epic™, Floor Pro Encore™, and Floor Pro) debuted in 1983 and has been revised since that time under these models:
Model B-9 (1983-84, 2-toned gray; 1984-85, sand sand/jade)
Model 1522 (1985-87 sand/jade; 1988, sand/taupe; 1988-92, lt. sand/navy)
Model B-10 (1987, sand/taupe)
*Model 1732 (1992-93, navy/lt. sand)
*Model 1739 (1993-94, navy/lt. sand)
*Model S105A (1994-95, navy/lt. sand)
*Model S105B (1995-97, gray/coal; 1997-98, oyster/fog)
*Model S105G (1998-00, oyster/fog--75th Anniversary edition)
*Model S105J (2000-02, lt. blue/white)
*Model S105L (2002-05, lt. blue/white)
*Model S105N (2005-07, lt. blue/white)
Model S165A (2007-09, lt. blue/white)
Model S165B (2009-13, white)
Model S165F (2013-present, black/white)
*The models 1732, 1739, and S105s had cord winders.
Its predecessors, the Model B-7 (1959-62 in lt. gray and aqua) and the Model B-8 (1962-83 in aqua, tan, teal, gold, brown, and dk. gray) might also be counted in the longevity for their similar designs.
TriStar's® ProStar™ (current Model S165D, white/gray) is a rebadged Floor Pro. The ProStars™ have likely been around since c. 1998 when TriStar® was acquired by Electrolux® LLC. I'm unfamiliar with its models and color variations.