Cloning Test Cases and Projects

As a result of having a lot of Services to test, I've had to create a number of Projects (about 10 and increasing) within LoadUI each containing a number of test cases (maybe 10-12). The more test cases I clone within a project, the more LoadUI appears to struggle to create them and eventually stops responding altogether. Then the file becomes corrupt and everything is lost. Is it generally a bad idea to clone tests too many times or to have too many tests within a loadUI project.? Or should it be performing fine at these levels?