If you're trying to do longitudinal research (with multiple waves of data collection), to create wave-specific variables with common names so that a statistical package can easily aggregate them.
At the other extreme, if you're looking to track changes in answers during data collection (e.g. to see if a person back tracks and changes their response to a survey), that isn't currently supported by LimeSurvey, but there are
working examples of data models that can support the collection and analysis of such data.