Just a quick thought:

If you put a lot of time and effort into creating something, and then you wanted to sell it in order to make some money, presumably you would not like it if people started passing it around for free without paying you, because they would be stealing from you.

I encourage everyone to keep this in mind, even when it comes to GMAT study materials. Remember, when you get to business school, you will almost certainly take a class about business ethics...

To answer the second part of your request, I recommend alternative between math and verbal every day or two rather than splitting them month to month, it is much better for retention.