To help clarify, here is what I'm working with and what I hope to accomplish:
I have quarterly MS Access files, all consisting of the different date ranges of the same data. Along with these, I have a running Access file that I append new data to weekly, which is then saved to a separate file when the quarter ends, starting a fresh new running Access file to append weekly data to for the new quarter. Rinse, repeat.
I'd like to combine the 6 already completed quarterly MS Access database files into a single Tableau data extract, and add the new data to it weekly as it's added to the Access file. I'd be happy to use an "incremental refresh" to simply add new dates from the running file, as long as I can get the other files in there first, and as long as the incremental refresh option doesn't delete data from the extract when it no longer exists in the source file (the running source file will reset at the start of each quarter to only include the most recent week's data).