Now that One Search is included in the price of Destiny, one should keep track of statistics. Currently there are not a time frame for the search statistics, so you may want to run One Search Database Usage Report periodically and save the results. Then you can subtract from previous results to get a time frame.
Do not forget to run other reports such as WebPath Express Statistics and Search Statistics to see what the students are looking for and what searches do not retrieve any results. You can use this to find material to meet these requests as well as learning how the students are using Destiny to help teach them proper search techniques.