Hi Sophie,
While there is no set "recommended" number of times you should check your watch, I tend to look at my watch at the end of each game (in LG) or passage (in RC). In Logical Reasoning, I check to see how much time I've taken to answer the first 10 questions (so, after Question 10), and then again after question 20. Ultimately, this is a personal preference: I typically find that if I'm constantly checking my watch, I start freaking out and lose concentration. You can't simply start thinking "faster" just because the time is ticking: if anything, it slows you down and you start to panic. For that reason, some students swear by never looking at their watches... which is also a bad, idea, IMO. You want to pace yourself well, but within limits. With enough practice tests, you should be able to find the right balance for yourself
Thanks!
