TL : DR stands for “too long: didn’t read.” The perception of what is too long clearly depends on the audience and the topic, but another key factor is formatting. Full disclosure here: my observations stem from experience rather than exhaustive academic study of the issue. However, I know that many people check out when they see a long screen full of text, or encounter a report without headings or spaces between paragraphs.
I’ve developed my own guideline: if you can put an American dollar bill horizontally over a block of text and see words on the top and bottom, that paragraph is probably too long. Readers may decide to skip it or skim.
Break up your writing into manageable paragraphs, and consider using “message headings” for sections* to boost skim value. Your readers will thank you – and might read what you write.
© Beth O’Sullivan 2019