What I have done in the past (don't know if this is the best way, tho) with versions dating back to Vue 7 is to create a "Vue Combo" folder where I keep all versions mixed together except the two most recent ones.  Each time there is a new version, I let the newest addition override the files with the same names from the previous versions.  However, I also keep a backup copy of the in-tact old library for each version.

If I have bought something in the older version (don't always remember which ones), I'll notice that it is for an older version when I try to use it and can then reset my Cornucopia account and thus re-download a copy, this time for the newest version.

With this method, I always have three libraries showing up in my content - e.g.: Vue 11 Library, Vue 10.5 Library and Vue Combo Library.

Hope that doesn't sound too confusing.  It has worked great for me so far.