There were several posts here and at the HP support site where people were complaining about IE memory leaks during long tests with many iterations. The advice that was given was to reopen the browser.
It was fine with me until I started to work with Web 2.0 (RIA) applications, the IE memory leak was so severe that it impacted a lot of automated tests.

I have decided to do a little research. I have done several tests against a somewhat traditional web application and against GWT-based (AJAX) web application.
Based on these results I had to modify my framework to make the test execution faster. I am currently enjoying about 25% test execution time reduction.

You can find the "QTP-IE Memory leaks" article on my company site: