QuoteTo me, what really distinguishes DeWitt from other commentators is that he seems to have devoted almost his entire professional writing career to the study and exposition of Epicurean philosophy exclusively.
It's beside your main point, but what I'm finding in my research is that his academic interest in Epicureanism may stem from later in his career than I realized. There is, first, his dissertation for Doctor of Philosophy at the University of Chicago; a study of the erotic in "The Dido Episode in the Aeneid of Virgil", 1907. He surveys the literature of Greece and Rome in laying the groundwork for his thesis, but one figure is curiously absent: Lucretius.
Excluding the above, his next six publications (1912-1924) are all on Virgil. Then an article on litigation and Cicero, followed by two history textbooks (1927 and 1934) for the curriculum in Canada.
After these, a course correction; at the age of 59, in an essay entitled "Parresiastic Poems of Horace" (1935), he writes on παρρησία (parrhesia, frankness of speech) as an unique virtue of Epicureanism. After this, essays on Epicurean Gratitude and Epicurean Kinetics ('37 and '41). Then a detour with his son through a cooperative translation of Demosthenes (1949), and right back to Epicureanism.
In 1954, Epicurus and his Philosophy and St. Paul and Epicurus are both published; it seems likely enough to me that he spent more than five years on these two texts, and may have worked on them while coordinating the translation of Demosthenes with his son.
One last thing at the very end of his life--an essay on daily life in Rome called "Vesta Unveiled", as part of a collection of essays published in honor of Berthold Ullman, a Classicist who earned his Ph.D at Chicago a year after DeWitt.
So most of the last twenty years of his life were devoted to the study of Epicureanism, most of his early career to Virgil.