I thought I'd add this topic as there appears to be a lot of confusion over whether or not there will be extra FBI checks if your spouse flies into the US while the I-130 is pending.
I've actually looked ahead at the paperwork required for NVC to check out the visits to the US situation.

The only thing I found was on the DS-230 part1 form ..... question 25. "List dates of all previous visits or residence in the United States (if never, write never) Give type of visa status, if known ....."

So, from this, I gather if your spouse flies in to see you in the US, it's ok until after you send in the completed DS-230 form .... after this, it would make sense that further checks may have to be done which may possibly delay your case a little ..... but again, this is just speculation drawn upon looking at the DS-230 form.

Please note that they only give you 3 spaces for you to list your visits ..... it's a nightmare if you've been travelling there for many years, and I myself, like a lot of you will be adding an extra sheet of paper to this

Do they give you a year-cap on the "flight information"? Like within the last 5 or 10 years? What are people supposed to do if they visited 10 years ago and already got a new passport and cannot look up the old entry stamps? just seem a little bizzare. It would definitely suck to track down the flight history for the last 30 years...

There doesn't appear to be a cap on the amount of time it goes up to ..... it just says list all of the previous visits .... they do just give you 3 lines to fill for 3 trips, but we all know that most of us are way over 3 trips .... yes, 30 years worth sucks real bad .... this is one time I actually get to blame my parents for something