Software is only supported for 4 years so even if you wanted to install one of those old programs you would not be able to updated it or get the state program.
Saving each year as both a PDF (with worksheets) and the .taxfile is a good idea. And at the end of the filing season you can also save the up to date program file on your own CD or thumb drive and it will be more functional than what is on the TT CD (which is just a bare bones beta version and totally useless without all the updates).
