The Search Assistant trial gives you 30 days of unrestricted use. At the end of 30 days you will need to purchase a license for $19.99 us. to continue to use the software.
System Requirements for Search Assistant
Microsoft Vista or Windows 7 or Higher.
Microsoft .Net Framework 4.0 or Higher (you will be prompted to install it if it isn't present).
Windows Desktop Search must be your default search provider.