Your improvement depends far more on the quality of your study than the quantity of your study. Doing that many questions is a very inefficient use of your time if your primary goal is simply to do a ton of questions.
You learn FAR more from analyzing, reviewing, and studying material than you do simply from doing a lot of problems. Maybe 15% of your learning comes from doing the problems initially; the other 85% comes from your review and anlaysis afterwards. I regularly spend 3 to 5 times as long studying a problem as I spent trying the problem in the first place - sometimes longer.
Read this article; it describes how to study problems:
http://www.beatthegmat.com/a/2009/10/09 ... ce-problemNext, you don't mention sources. The Official Guide is the best source, especially for verbal, and the source is very important. You want to study from one of the better sources available. If you are studying from, say, a compilation of materials from unknown sources that you found free on the Internet... well, I've looked through such sources myself and I personally wouldn't use them.
Finally, you don't mention anything other than a source of practice problems. How are you planning to learn the grammar and the various techniques that you need to learn in order to improve? This doesn't come easily from trying problems. Generally, you need a source of instruction that teaches you these things - whether that's books or classes or whatever.
You may want to read this article:
http://www.beatthegmat.com/mba/2010/02/ ... study-planThe good news? As a general rule, if you (a) are working from high-quality materials, (b) have adequate sources for both instruction
and practice, and (c) are focusing on analysis and review, then you don't need anywhere near the number of problems you listed in order to get to the 600 to 650 range (though this does depend, to some extent, on your starting point). :)