Howdy,
For a room not classified/certified as a cleanroom, you don't HAVE to do anything. So I'm not sure the basis of the question.
For my ISO8 (100K) and ISO 7 (10K) rooms in the past, one reading was done per location by an outside body as per the previous post above. This was done once per year.
If you want more data, you'll get more usable data measuring the room more often than you will measuring 5 times in a row in the same day.
Given the choice between 5 measurements the same day each year, vs. one reading per location each quarter...I would take the quarterly (it would cost more, though).
Sampling the room once in full usage condition will tell you all about the room...measuring it again 2minutes later gives you no additional useful data unless the first reading is way outside of expectations.
HTH