When you setup a scheduled export from Funnel it will export and overwrite all your data each time it runs. Here are three reasons why.
The nature of advertising data
Advertising data often takes between 7 to 30 days to stabilise from when we first download it. For some platforms and configurations it could take up to 90 days. There are several reasons for this, one being the attribution model. You can read more about this here.
Adding a new data source
If you add an additional data source, Funnel normally pulls in two years of historical data. That would then need to be fully back filled in your export.
Changing your export schema
If you, for example, want to add an additional field to your export from one of your sources this will change the schema. To make sure that the new schema matches with the full history of your data, a full back fill needs to be preformed.
With the above in mind, we recommend exporting a full set of data at least every 24 hours.