i agree with pansity that the presence of servants is "implied" rather than having the characters actually appear on screen.they frequently get mentioned in most time periods.
the exception would be the present where it is clearly established that liz dismissed the entire staff eighteen years earlier and since that time only matthew morgan,and later mrs.johnson,are the only servants in the house.
speaking of mrs.j. such is her devotion to the collins clan that it is easy to forget that she actually first came to collinwood to spy for burke devlin and help him bring down the family.
i remember once in 1795 some sort of hatted maid delivered a note to millicent.
in 1970pt there also is apprently a full staff.besides a maid(hoffman) and a butler(trask) there is talk of a cook,a gardener and several chambermaids.again these characters go unseen.