Here are some good reminders re scholarship from Rethinking the Synoptic Problem (ed. David Alan Black and David R. Beck; Grand Rapids: Baker, 2001), emphasis added:

1. Scot McKnight, “A Generation Who Knew Not Streeter: The Case for Markan Priority,” p. 66:

The unfortunate, however unintended, implication of coming to grips with modern scholarship is that in learning contemporary scholarship, students put the previous generation on the shelf. These scholars are sitting there full of chat, but, sadly, modern students don’t have time for older studies, and so the books become forlorn as the faces of the scholars become lonely, sad, and unknown. It is a fact that modern scholarship’s improvements do not necessarily make older scholarship obsolescent.

2. Grant R. Osborne, “Response,” pp. 150–51:

There are no certainties in life. It must be said that scholarship, like all other earthly endeavors, runs in fads, especially in the post-Enlightenment setting. Scholars are essentially Athenians at heart, always searching for some new thing (Acts 17:21).  The four-source hypothesis [which Osborne holds] has dominated for almost a century now, and that is a fairly long time. So we can never know when some new genius will come along and establish a new theory that will carry the day. However, it is the purpose of symposia like this to sum up the “state of the art” on the issue, and I believe we have done as well as we can. It seems to me that the evidence points clearly to the modified Streeter theory that Mark was first, and that it existed alongside a sayings source that we now call Q. Later, Matthew utilized both and supplemented them with his own (M)emory material. At the same time (it is nearly impossible to know which was first), Luke used Mark and Q along with other sources he had gathered (L), and wrote his Gospel. Again, certainty is impossible, and it is good for us to be “iron sharpening iron” as we debate the proper approach to interpreting the Gospels on the basis of the sources they used (redaction and composition criticism). The only mandate for all of us is humility. We need each other, for without these challenges we become arrogant and falsely certain of our community-shaped theories.