There is no way to delete data from a TDE file, so you will need to recreate the extract with the last x weeks of data.
But there is no need to swap extracts or change any configuration - you can just define the extract with a relative date filter for the last x weeks. Then each time that you hit refresh you will get the most recent x weeks worth of data.
Does that work for you? Was it just the hassle of refining the filter and the connection that you were trying to avoid - or were you hoping to save time by just adding the most recent week and dropping the oldest week?
Ah-ha - cool. I haven't yet played with the relative filters, so sounds straight forward. Thanks