So the obvious question is ... are there ever multiple short-duration surveys that can be put together to create a dataset covering a longer time-span?
Since short (3-4 year) studies are not sufficient, it would make sense for specific institutions/universities to set up long term studies whereby grad students would conduct a study for one period and then another would take up the study for the next period. They would each write their thesis, and these studies could be conducted for decades so long as the organization kept the flow of PhD candidates following the long term studies.