Yes keep a backup of your Pro installers. Also, Bookmark your personal pro download page. Near the end of your pro period, on that page it will tell you that you are in your last part of support & offer a discount to continue.
Jumping between Basic & pro can sometimes cause issues with the preferences. Make a note of all your settings, & delete your LW Preferences folder whilst LW is closed; instructions here: Point #2 & 3 in Fixes for Limewire (sample image included at bottom of page.) Keep in mind next time you open your LW it will ask you about resetting your options so be sure you make a note about all your previous settings before deleting your LW prefs folder. Days to keep incomplete files is an example of one that needs to be changed.

LW is now up to 12.14.10, not sure if you wish to upgrade to it or have already. Alternatively, reinstall a version you know works ok for you.

One other point is many pro users have had problems with Java 1.6. You many consider removing ALL java versions & stepping back to re-install the JRE 5.11 offline version Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 11