Mammoth Uncensored Word List:
32 words ending with es, 21 letters long

acetylcholinesterases anatomicophysiologies buckminsterfullerenes colpoperineorrhaphies contemporaneousnesses disadvantageousnesses electrocardiographies electroretinographies episioelytrorrhaphies extraterritorialities hypersusceptibilities immunocytochemistries immunoelectrophoreses incomprehensibilities interchangeablenesses interconvertibilities isopropylcyclohexanes isopropylcyclohexenes meningoencephalitides meningoencephaloceles multidimensionalities otorhinolaryngologies perhydrophenanthrenes polyhydroxyalkanoates pseudocholinesterases salpingoophorectomies sigmoidoproctostomies spondyloarthropathies straightforwardnesses unconstitutionalities undemonstrativenesses unexceptionablenesses