What's your codec of choice (besides cineform) on the Windows platform for exporting a finshed copy of your project? Essentially this would be your master.
I use lossless UT codec .avi files for archived masters.
Lagarith is also lossless, and good for archiving .avi masters.
Avid's free DNxHD is free and widely used - the latter may offer some sort of future proofing.
Unlike UT or Lagarith, it is not lossless, but is regarded as master quality. Like the two Jim suggests it does give much smaller files than Lagarith or UT.
On the downside it is Quicktime based, rather than AVI.