perpetuarius
From LSJ
perpĕtŭārĭus: a, um, adj. id.,
I constant, permanent; always employed, constantly engaged in any business or calling (post-Aug.): mulio, Sen. Apoc. 6, 2.—Subst.: perpĕtŭārĭus, ii, m., a fee-farmer, hereditary tenant, Cod. Just. 11, 70, 5.