General Question: About the 'using' statements.

Question

Hello:
 
In my Forms I have about 19 'using' statements. When I create a new form I just copy the whole list of the 19 that I have in one form.
 
1. Is there a way to find out which 'using' I don't need in a specific form?
 
2. If I have too many of them, does it use more memory that is not needed to be used?
 
3. I might have 50+ Forms in the project when I am done. If I have too many 'using' with this not degregate the performance?