Lewis and Short, in their entry on ab, describe a shift in use of abs in Cicero's works that had far-reaching ramifications:
The use of abs was confined almost exclusively to the combination abs te during the whole ante-classic period, and with Cicero till about the year 700 A. U. C. (=B. C. 54). After that time Cicero evidently hesitates between abs te and a te, but during the last five or six years of his life a te became predominant in all his writings, even in his letters; consequently abs te appears but rarely in later authors.
Do we have any indication as to why Cicero's preference changed over the course of his life? Did he or his contemporaries suggest that abs te had come to represent poor style? Do any subsequent grammarians, particularly those of the Late Latin era or before, suggest any explanations for Cicero's shift?