Sorry to burst your bubble, but that sounds like an absolutely awful strategy. If you make any "unforced" errors in those last 30 questions, your score will be terrible. Prateekbhatt is absolutely correct: start strong, convince the computer that you're awesome, and if you have to take a few lumps toward the end of the section, it won't hurt your score too badly.
If you're really curious about oddball guessing strategies, check out this thread: gmat-prep-software-analysis-and-what-if-scenarios-146146.html
. A similar but older batch of GMATPrep experiments can be found here: un-scientific-analysis-of-gmatprep-64970-100.html
Helping students kick the GMAT in the nuts since 2002... www.gmatninja.com.