The answer is, of course,    It depends.

Are you going to ever use that data for something else? Then don't delete. Are you exiting as soon as you find the stuff you want and operating on it? Then don't delete, you're just wasting the CPU's time when its ALL going to be deleted from memory when the program exits anyway.

The ONLY time deleting makes sense is if the script will continue to run, and it's accumulating a lot of stuff, and continuing to operate on all the "good data". If this is the case, then yes, deleting the non-useful information will save memory, and is thus a good idea.

-Scott