It depends on the source of Verbal practice you're using. I find with Kaplan verbal (bleh!) it is quite useless to go back and check why you got it wrong. This is simply because Kaplan's questions are almost all fact-related to the passage, so you can easily see why you missed.
I went over the questions more so when I first began doing verbal, because I was averaging about a 28/40. Now, however, I'm at about a 34/40, and when I look at what the answer is I usually say to myself, "Oh, okay, that makes sense." To me, there is no need when you feel this way. However, if you're missing the same type of question over and over again it would be useful to go back through and see what errors you're making.
It depends on how well you're doing. If you're scoring 38/40 on average, then it would probably help to really pin down those details as to why you're missing what you do. Otherwise, you can improve verbal through PRACTICE, PRACTICE, PRACTICE.
By the way, these are my favorite verbal materials:
1) EK 101 Passages*
2) The Berkeley Review Passages
3) Kaplan
*I have TPRH Verbal Workbook, but I'm saving towards the end of studying so I can use them to my full advantage. I've heard they're the best.
I like to do different sets every day. This way I don't catch on to a particular type of style. If you want to feel good about yourself, do TBR passages. If you want to feel horribly, do Kaplan. I despise Kaplan, but alas, it's still practice.
Good luck, OP.