Usually, it is said that number of critical questions related to the test, should not be more than 10. It is a result of phenomenon called ,,anti-climax’’. It is a significant decrease of reliability of the measurement of the reaction on answers, which are gradually mashing up in large number of questions. As a result, it is recommended to divide performing this test on longer period of time if there would be more questions. Of course, the test can be performed on one time with large number of questions, however there is no guarantee about the reliability of results of such test.
Exception to this can be test that are having as a target determination of personal history of certain person. In that case, sets of question can be larger.