IMO, i don't think you can treat the GMAT the same you can treat a final exam. personally, even though i had a lot of free time during my gmat studying, i limited it to 2 hrs~ per day (except on days that i took full length tests, in which case it was 3 hrs).
a lot of the GMAT isn't necessarily knowledge based (like memorizing equations/formulas, definitions, dates); rather, it's more about having a good background knowledge of all of the materials, and then applying good test taking skills (pacing yourself, knowing when to skip questions, not freaking out) in order to do well. this can only come through practice practice and more practice to gain stamina and familiarity with the test.
so, to answer the OP's question, i'd say don't overdo it. just because you can dedicate 10 hours a day to the exam doesnt mean you should. as with most things in life, i'd say have a healthy balance and dont get stressed out by the exam prep.