It is difficult to quantify a maximum number of questions in a Question Set because the 'size' of a question set is determined by number of characters/letters which relates to the lines of code/text of the full Question Set. Images and other attached material (pdf, video) create one line of text each for a question. 

Typically < 500 questions in a question set are accommodated, but please bear in mind that this number will vary if there are longer or shorter text questions in the set.

You will not be able to add more questions to a Question Set if the size upper limit has been reached and may receive an error message such as "Invalid session, your session has been invalidated. Try reloading the page". Please remove questions or contact Service Desk for assistance.