Let's suppose that you install a 30-day limited software on July 3rd... You went on holiday from July 5th till August 19th. When you come back,
you see that this software can't be launched anymore (the trial version has "expired"). Do you think that 2 days are enough to try a software ? I don't.
There would not have been any problem if you had used Independence Date. You would have configured a button, with the following settings :
Caption : any
Program to launch : enter the path to the software or use the open dialog
Year of launching : current year
Month of launching : 7 (July)
Day of launching : 4 (or 5,6...)
Don't forget that you must uninstall or purchase the time-limited software when you have tried it during 30 days.