No, its not silly at all. If you get a theme from a .jad file or .jar, you can use a program to save them to the media card.
Originally Posted by westiewanderer
You need OTA Downloader on your Blackberry to save the theme files, and a free file manager will keep all the themes in one folder on your memory card.
Rock File Manager v0.9.2
OTA Downloader For BlackBerry®[Full Version] | My BlackBerry
If you buy themes from App World or MyBBOTA, you can't save them with OTA Downloader, so those are the ones you will need to back up with BBSAK, and BBSAK can re-install the theme from your PC if you accidently delete a theme.
Edit: The BBSAK backup will also save a copy of all your OTA themes on your PC in case your BB is wiped, or you have a media card failure.