Time per question

The reason that different experts will give you different advice on how long to spend per question is that everyone's timing will be slightly different. One student might take longer on CR to unpack the argument, but move faster through SC. Or, she may decide that since her SC accuracy is lowest, it makes sense to sacrifice harder SC problems to spend longer on CR. That's something you'll have to decide for yourself.

Here are the general guidelines that I give my students:
PS: ~2:15 min on average per question
DS: ~1:45
(although for some students DS takes longer to think through)

RC: 2-3 min to read the passage, 1:30 per question
SC: ~1:15 per question
CR: ~2:00 per question

Really, though, you should take several practice tests, and see where your accuracy is highest and lowest, and base your time on your own personal needs.