It is rarely useful to clear variables in the workspace. In many cases this decreases the speed. Prefer a proper pre-allocation, such that clearing is not required anymore.
30 Variables are a lot for a loop. Remember that a high code complexity reduces the readability and maintainability. The need to clear variables might be a secure signal, that the complexity has grown over a certain limit. A solution would be to move the body of the loop into an extra function. Then the smaller piece of code is easier to test, to modify, to debug and to maintain, and in addition the workspace is kept clean automatically.
