Timing is a HUGE factor in verbal, far more than the other sections for most people. That's why it's best to practice under stricter conditions than what you'll face. You need to get in a rhythm where you consistently have extra time. On the actual test, that extra time will act like a buffer against the stress of the real thing. Additionally, the current MCAT has longer verbal passages, by about a paragraph, which will further eat into your time. Most of the people that have practiced under strict timing have been glad since they used up quite a bit of it for the real thing (usually left with only a few minutes). Conversely, people that typically struggle in verbal have a very difficult time finishing before the clock runs out. Almost all of the threads I've read where people are doing poorly in verbal mention timing being the biggest factor. Getting in the habit of finishing minutes before the clock runs out on the practice tests will probably hurt you for the real MCAT. Overall, practicing under strict time conditions helps to ensure that timing won't be much of a problem.
Here's what Vihsadas wrote:
1) Practice under harsher timed conditions than you will encounter on the test. You will have about 8.5 mins for every verbal passage. Get a stop watch and a verbal workbook, and practice finishing every passage in 6.5 mins. When I started doing this, two things happened: 1)Even though I was using less time, my scores did not decrease. They stayed the same. 2) When I became really good at answering the passages quickly, I found that I had time to refer back to the passage on every question. Now, since I can read the passages much more effectively (meaning faster) when I see a question that I'm not sure of, I have time to go back and quickly re-read the 3-4 sentences that pertain to the question. At this point, my scores started to increase.
If you want some more people recommending strict timing, check out the study guides in the MCAT Guide sticky thread or the 30+ thread. When people mention timing, they typically suggest harsher conditions.