Can somebody tell me if this deck has "locked" audio when converting analog to Digital? And is there anything that I should know about the JVC SR-VS30U for analog to DV conversion?

I use mine all the time for converting S-Vhas & VHS to digital. Sometimes I dub a tape to DV, other times I use it as a capture device for my editing system. I also use it for capturing other formats (Hi-8) through the S-Video inputs.

Does the audio ever go out of sync with the video when you convert a long program from analog (VHS, S-VHS, 8mm, Hi-8mm) to DV?

I've never had that problem. If you are using a monitor off the deck outputs, but are listening to your computer speakers, there is a lag, but it is in sync when captured and output. Try turning off your computer speakers and watching and listening to the monitor (I just use a small TV) On my system they are in sync.

It isn't the deck that determines locked or unlocked audio, it is the format. DV is not locked audio by definition.

Most of the companies have learned to do the audio correctly with regard to syncing with the video. AFAIK, only Canon really were 'out of sync' with the rest of the world.