To return to a question asked earlier:
How much data can be stored if running the program 24/7?
i.e. does it accumulate in a log file somewhere, or is it overwritten as a maximum sized data "window" in memory?
The only limit is available memory. By my calculations, if you sample every 30 seconds you'll be holding about 1.3 MB of data after a week, so there isn't an issue there at all. It's possible that there could be some speed issues with scrolling when a very large number of points have been plotted, but that shouldn't happen within any realistic time frame.