It needs a double scroll (both horizontally and vertically) to fit for example the 16th century in.
If this were difficult you could assign sites above a 1 page maximum depth to "dummy periods" with the same title - either randomly/alphabetically or split them by Europe/Asia/ROW.
So for instance you would get 3 vertical columns for 16C (each called 16C) with 30 max in each - not ideal of course
Sites would still appear with a correct century in their own page.
Which raises another question - a "click" on a timelin entry for an individual site would need to take one to the correct column in the width of the new page -but is this any different from taking one to the correct "depth" which I am sure is done now sometimes?
Or you could leave the timeline entries in Connections as now as well?