I find that the response is rapid, usually within the hour during the day, but can be slower if you post on the weekends or middle of the night (I have never needed to do this thankfully). Considering the support is free you get a lot more than I would expect. The speed of the answer usually depends on the quality of the question, so include as much information as possible: version of labview, hardware resources, specific concerns ...
One important point - this place is run by NI and I believe NI does have an internal policy on answering questions, but most people here are private people who do this on their own. As suggested, if you post an interesting question (or even a simple one, but display the problem accurately and show that you're willing to do your own work), people will usually try to answer it.
Another important thing is to search before you post. This place (as well as the LAVA forums and the info LabVIEW mailing list) has a lot of data already in it and often questions have already been answered numerous times, so really try searching first.
Well, there are no guarantees. 😄
If you look at the names, there are regular guys and blue guys, the blue guys are NI people. Regular guys such as me are just volunteers trying to help out because it is fun. There are many contributors with 10+ years of LabVIEW programming experience, so the collective knowledge and intelligence of this board is quite high and it is very likely that you'll get an excellent answer pretty fast. Participants are from all over the world, so even at your 2am it will be a more reasonable time somewhere else.
Next to the name are some yellow (or blue) bars that indicate seniority based on the number of posts, ratings received, etc, so if there are multiple answers pick the one from a more trusted source.
As in real life, the quality of the answer is strongly dependent on the quality of the question. Start with a captivating title related to the core of the question and not something generic such as "please help", labview question", or similar. Explain your problem as detailed as possible, what you are trying to do, what results you expect, what errors you see, etc., not just "it does not work". Many times it is easiest to attach a simplified version of your program. Make sure to put some annotations on the diagram pointing out the problem you see. Put some reasonable default values in the controls so we can run it with real data.
So, just go ahead and ask, it's free! 🙂
Of course there are also premium support options if you want more traditional support with case numbers and live telepone help. Contact your NI rep for details.