asiduo

adj. assiduous, diligent; regular

n. habitue

= heavy [heavier -comp., heaviest -sup.], regular, assiduous, habitué.
Ex: A leased line connection is useful for heavy users, since it offers higher speeds of transmission.
Ex: Book form was generally regarded as too inflexible for library catalogues, especially where the catalogue required regular updating to cater for continuing and gradual expansion of the collection.
Ex: The management of a large number of digital images requires assiduous attention to all stages of production.
Ex: Morris writes rhapsodically about celebrity-studded parties, roistering interludes with major writers and artists, as well as gossip-column habitues.