Using some (partial dates not included) of the data you've generated from transcribing playbill dates, I've created this (very basic!) bar graph to illustrate the range and popularity of dates for performances by year. As you can see, there appears to be a huge spike in 1825 and I'd love to discuss why that might be!
Aside from the growth of Britain in general (London in particular is one of the biggest cities in the world), railways, the extravagant influence of George IV etc, does anyone have any ideas or thoughts on what could have caused this? Even taking into account aspects such as the influence of the playbills' collectors and their origins, the increase of performances in 1825 is noticeable. I'm going to take a look through resources such as UMass's Adelphi calendar (https://www.umass.edu/AdelphiTheatreCalendar/m25d.htm) to investigate this today, but would love to hear your thoughts or insights into what might have been happening in 1825.