This does not answer your question, but it is usually preferable not to have vertical relation symbols, and not to worry about the vertical alignment, except at the first equals sign (this is done with "align"). Instead, you usually want things more like this:
A ~ B ~ C ~ D ~ E ~ G ~ H ~ I
and so on.
More to your question, I know there is a way to save an alignment place and recall it later, but I don't remember how to do it. Another option might be to use the "split" environment.
Sorry I couldn't be of more help. An excellent resource for these kinds of questions is this book. Good luck!
More Math into Latex is excellent. You can get the short course (first few chapters of the book) free here.