Marvel editor Ralph Macchio weighed in on the subject of continuity in the Original Marvel Universe on the letters page of Thor #364 (February 1986):
Most of the original Marvel characters from the sixties are still thriving, and we intend to keep them that way. What we don't want to do is embalm them. Change and growth are essential. In a comic book that runs a long time, you're likely to have antagonists coming around again for the zillionth time--and how many times can you believe that the heroic Purple Pantywaist will take the menace of the terrible Tape Dispenser seriously since he's already beaten that nasty villain 37 times? ...So you search for ways to bring back old guys without simply retelling the old stories. Because if the readers begin to feel like they've read it all before, they'll start reading something else! And no worse fate can befall a comic book!
It's too bad Marvel lost sight of this sensible approach a few years later, locking their characters into a continuity merry-go-round that continues to this day. No growth, no lasting change, and embalmed "iconic" characters that fight the same fights over and over with no sense of history.