Here are some thoughts on my limited experiences. 3 tests back I could barely handle the time pressure but now I have developed/improved my timing.
- how can I improve my stamina as I enter into the last phase of GMAT preparation?
Use breaks appropriately - alimentation and hydration are key particularly between the maths and quant. Motivate yourself - look forward to a particular activity post test (tonight im going to have a couple drinks/poker game/dinner with gf) - keep yourself motivated you should be pumped for every SC as its a quick and easy time saver theres gonna be like 17 of them! RCs just feel like your in HBS and you gotta read 4 lousy small 200-500 passages you can definitely do it. Don't look at the 4 hours as a burden look at it from optimistic point of view you trained you practice all the summation of everything is now going to be reflected in this... act like you love it, if you do great if you don't appear like you do. The test taking skills, like other facets of life, acquired so just enjoy it. Just like when you practiced something so much for X amount of time, come performance day (soccer game for example) if you were good and you liked to do it you shined.
- how can I improve time management on V?
As walker suggested, SCs are the key, SCs appear in volume and they can be tackled methodically, confidently, and quickly. They are essential. For CR do you know the strategies, do you map out every argument? Have a fixed approach... read the stem, question, choices... or read question, stem, paraphrase, eliminate, select between 2. Save time by having flexible fixed approaches. Know that for every CR you will adopt a question stem based approach yet have different strategies for weaken, strengthen, paradox, inference... For RC, skim, read, comprehend, always under 3-4 minutes - after all the questions of RC are pretty formulaic in the GMAT so the more you practice the more it becomes second nature. MAP the argument should be more basic than it seems - I think you should have an idea of the reasoning and the chain of ideas but too much details is not necessary as after the questions you will go back (I struggle myself in this area at the moment, so take my suggestions with a grain of salt). The really good thing about RC is its GMACs gift from god after all its fixed bank of questions- the answers are right in front of you( 12-14 of these sounds like business).
If you read here, I find BB time management strategy for verbal very polished: gmat-study-plan-go-from-650-to-80235.html
Hope it helps and great questions. I can certainly improve on both aspects.
All the best,