I think that depends on your ability to diverge your creative thought processes.
Generally I wouldn't encourage it, and commit your efforts to one at a time to ensure quality. Do you think that you would work to the best of your potential?
Do you keep a notebook or diary or something of the kind? If not, I suggest you do so you are able to keep track of your thoughts and ideas. Write your other ideas in there whilst you finish so that you won't lose them
