DPA does have a threshold for the number of queries that get summarized. By default, it only summarizes the top 500 queries based on wait time. This can be increased by changing the support option "TREND_MINRANK" to something higher. However, increasing this value also means that your repository will grow.
To change the TREND_MINRANK value, click Options, then the Administration tab, then click the Advanced Options button. On the System Options tab, check the "Support Options" check box and search for "TREND_MINRANK".