Did I goof by not downloading all the individual pieces that were "current" during the time my license was active?
Typically, yes. The traditional OD Subscription model always meant it was wise to download anything you needed and keep on your machine as a hard copy, particularly if you allowed the Subscription to lapse/end.
If you had no intention to cease the Subscription you would still lose old versions being accessible unless you had DL'd them first as Stardock would update and/or release new versions, displacing the old....
Example... this machine is Windows 7 so there has been no great urge to update beyond what was original/specific to 7 way back then, and as with all installed proggies I retain installers for them ... 