A survey may be repeated at intervals to validate data and measure how perceptions have changed. Often the results of a particular survey may raise further questions which lead to additional research on a specific issue.

Depending on the purpose of the survey, its usefulness and the ongoing relevance of the issues surveyed, it may be repeated over time or amended to provide particular information. ‘Core’ questions enable benchmarking over time, whereas additional questions can be used to respond flexibly to new circumstances.