Agreed. As one also championing a thread covering music for beginners, I early on discovered that TIME is irrelevant in terms of music history (or just plain old history for that matter).Very nice, and not ridiculous. Actually, I think your time schedules for the various periods are good. One can easily spend a month exploring diversities in Medieval & Renaissance music only, and get the big picture, for example - but even if including both the music and performance-wise, differences will be bigger later. The 20th-21st centuries have seen more stylistic diversity than anything else. Also, the earliest music is really tied up with, and dependent upon, the performers and their chosen performance style. You could then explore the various ages and performers in depth later too.
Medieval music is simply not as plentiful as music from later eras, especially Baroque, Classical, and Romantic. Most of us here that listen to Classical Music generally listen from these three eras, although there certainly exceptions (those who listen to lots of pre-Baroque or post-Romantic instead).
Chilham's set up makes a great deal of sense, especially from a teaching perspective: two months for Baroque, and three each for Classical and Romantic eras.
And, as with my Beginner's Guide thread, I am discovering along the way.