That's correct; the trial version of Songsmith allows you to use it for six hours total. Reinstalling the software on the same computer does not reset the clock.
In general, the answer is "if you love Songsmith and want to keep using it (huzzah! we love it too!), you'll need to purchase the full version of the software", though as per other threads in this forum, right now Songsmith is not available for
purchase due to some technical issues. Working on it!
Hope that helps.
-Dan from the Songsmith team