While I was working on Printing and Prophecy, I spent some time trying to visualize the publication history of the prophetic and prognostic texts I was working with. It turns out that timelines are not easy to create as Excel graphs, but after hunting around for a while I found a workable approach.
The preservation of practicas and other early modern ephemeral printed texts is pretty spotty. We have to assume a large number of missing editions. It's not too much of a stretch to assume that authors published one practica annually (although some surely skipped years), and that the career of a practica author spanned the years between the first and last known edition (although there were undoubtedly earlier and later editions that are unknown today). With those assumptions and caveats in mind, we can place the careers of German astrologers who published practicas in order from earliest to latest up to 1550. We get the following picture (which ends up being totally unworkable as an illustration for a printed book, unfortunately).
View the image above by itself for a slightly larger and clearer version.
What I like about this graph is that it illustrates quite clearly the significance of Johannes Virdung. His career overlapped with every earlier German practica author and with younger colleagues who continued publishing into the 1560s. Only with Simon Heuring, Joachim Heller, and Christoph Statmion do we get a generation of astrologers who knew not Virdung. Not coincidentally, I think, the German practica format remains exceedingly stable until after 1550, when the calendrical material gets moved again to the beginning chapters in many practicas. Virdung ensured his lasting influence by outlasting all his contemporaries and most of the next generation.