Hello
studyeagle,
Thanks for raising a valid concern. As you mentioned that you have been studying for GMAT for sometime now and you have not yet experienced the full length yet, its high time that you take your First GMAT Prep moc test right away.
Appearing for GMAT Exam is a test of endurance, and trust me even if you are an expert in Quant and Verbal but have not been practicing the 4 Hrs test in real test like environment, you may end up scoring low on GMAT.
Also, I would suggest, that only 2 GMAT Prep mocs is not a good option, you can purchase Veritas or Manhattan mocs (Both have schemes regularly where you can purchase 10 mocs for approx $10-$15)
Also note, that you can attempt the GMAT Prep mocs multiple times (after restting) which will give few new questions from the database. Though few questions will be repetative for you, but that should be fine as you will be exposed to more 600-700 level questions based on your score.
Keep your second GMAT Prep test for last month and then keep on practicing it.
Hope this clears your doubt. Wish you all the Luck for your exam
studyeagle..