Mammoth Uncensored Word List:
13 words ending with hs, 19 letters long

duotrigintillionths electrocardiographs electroretinographs octovigintillionths quadragintillionths quinquadecillionths septendecilliardths septingentillionths septuagintillionths sestrigintillionths tresvigintillionths undecicentillionths unsexagintillionths