The internal buffer can only hold ~32000 points total, so as you said you are limited to about 30 seconds of data acquisition at 512Hz sampling rate. The other problem is the output buffer is small, I believe something like 256 characters, so downoading all the points is slow also.
To make things continous, I believe you would have to experiment a bit with a circular buffer. Set the instrument to continously record points, rewriting the old data with new data in its internal buffer. You would have to write something in LabVIEW to download data every X seconds to keep up with the data flow, along with keeping your position in the buffer. (Do not download all the points at once, maybe 1-2k at a time.) How fast you can do this depends on your setup. (I'm not even sure this possible. I meant to try this with my own instrument, but never got around to it.)
Lastly I believe the FAST mode is for single point acquisition as fast a possible; your points may not be evenly spaced in time.
Cheers,
mcduff
