For me, it depends on the author.  If one of my favorite authors has a series,
I will usually tear through the whole thing if it gets dull.  A couple of
times I have been pleasently surprised with parts of books or entire books I
would not have wanted to miss.  On the other hand, an author I do not care for
or have never heard of doesn't ususally merit me beginning a series at all
(too much time commitment) except on the recommendation of a reliable source
(such as this list).  For instance, I immensely enjoyed Ender's Game (Orson
Scott Card) but I was not too thrilled about Xenocide...the third book (whose
name escapes me) was enjoyable, as was the fourth.  A counter example of this
would be OSC's Earth... series.  The first three were okay, but the last two
were IMHO terrible.

Kamikasee

In a message dated 98-05-23 13:34:03 EDT, [log in to unmask]
writes:

<<
 Just commenting on the "duty" part. Do any of y'all also feel duty-bound to
 finish a series even when the material begins to get uninteresting? >>