Mammoth Uncensored Word List:
10 words ending with hs, 22 letters long

chemolithoheterotrophs electroencephalographs microseismometrographs nonagintacentillionths octogintacentillionths quinquavigintillionths septentrigintillionths sexagintacentillionths unquinquagintillionths unviginticentillionths