For problem practice with the OG, I timed myself every time. I usually set a limit of two-minutes. But that doesn't mean that I would quit the problem once the time limit had been breached. I would finish the question but mark it as incorrect, citing "time" as the reason in my error log
. I would revisit the question sometime later in the day or the next day. (If I had no idea how to answer a question one or two minutes, then I would usually stop.)
I think that it's very important to get a sense of the test's time constraints as early as possible, so time yourself from the beginning with practice problems. Finish the problem if you can, but time yourself. You want to mimic the test conditions as best as you can. Some people even prop the OG books up vertically and practice at a desk with a test booklet and marker to better simulate the actual test experience.
Let me frame my reply another way: let's say that you can answer a math question in three minutes. If you go easy on yourself, then you will mark it as correct and move on. In this case, it's possible that you will forget about the problem and not review it. It's correct, right? But this masks the difficulty that you had with the problem. View any struggle with a question as an opportunity to improve and learn. Marking a question as correct when it's not 100 percent correct deprives you of the extra value from reattempting the question later on.
Another issue about timing is that sometimes people fail to adjust during their studies. If a question takes 2.5 minutes to correctly answer, then no big deal. But what if this happens ten times? During problem practice it might not seem like a huge obstacle, but it will during the test. It could also be a problem toward the end of your studies, since this deficiency takes time to correct. So why risk the chance of this issue creeping into your studies or occurring during the test? And why go through the additional hassle and stress of adjusting later on in your studies? It might be better to condition yourself from the start. That way, there's one less thing to worry about.
Again, you don't have be hardcore about it. But be aware of your time and give yourself the opportunity to improve right from the start.
GMAT Club Premium Membership - big benefits and savings