To run an old document faster, and use the new features of LaTeX2e, you should try using LaTeX2e native mode. This is done by replacing the command:
However, some documents which can be processed in LaTeX 2.09 compatibility mode may not work in native mode. Some LaTeX 2.09 packages will only work with LaTeX2e in 2.09 compatibility mode. Some documents will cause errors because of LaTeX2e's improved error detection abilities.
But most LaTeX 2.09 documents can be processed by LaTeX2e's native mode with the above change. Again, the easiest way to find out whether your documents can be processed in native mode is to try it!