Just a bit of "color-commentary" here:

A number of authors have written that the Red Baron suffered not only physical trauma from his wounding in combat on July 6th, 1917, but as result of this near-death experience he was finally forced to realize that even through disciplined observance of the "rules" of combat, no man could ever wholly guard against the eventual day when luck turned against him. In the heady days of his ascension in combat, Richthofen at times felt comfortable to deride the fact that some of his "gentlemen" opponents in the Brit "barges" dared to fire at him from ranges he considered too far to be effective, this to the Baron reflected the nervous action of a rookie gunner, and foolishly signaled the inexperience of his quarry. To a degree, the arrogance of his well-earned knowledge and fame came to a stark collision with a head-grazing .303, and forced-realization that no man is invunerable despite what his intellect might lead him to believe!

Many contempoary's of MvR, and experts about the man's life, say he never fully recovered from the physical and psychological effects of an errant bullet fired from too far away to be of concern.

MvR did observed and teach Boelcke's rules of closing up on the enemy before firing, even though by all accounts he was a superb shot as was Guynemer and Fonck. At times he would fire at longer ranges hoping to cause a faster opponent to begin evasive maneuvering prematurely (not against 2-seaters though), but as a tactic of closing the distance on his target.

Generally, I think most would agree that long-range firing in WWI was discouraged by the experienced air fighters, but even the experts could fall a-foul of the seemingly most improbable of odds (and the laws of nature).