In reply to gopal_susarla:
It is always better to run multiple shorter tests than it is to run one long test. This is because if you find an error, you can get to the failure point quicker for debugging and re-testing. I would recommend running separate simulations for each set of parameters.
Also, never use assert() with a randomize() call. This is because it is possible to disable assertions, resulting in your testbench failing without warning. Instead, you should use an if() statement to check the return code from the randomize call.