The feature causing this can be disabled in Preferences->Basic Settings->Disable Quality Reduction. Only question is if this is a good idea. You need high update frequency to get communication going fast. If your update frequency goes below a treshold the host reduces quality to keep up a good speed and safe your print. Disabling this protection mechanism might this cause problems with print quality.
Normally a 30 minutes print can be handled by current hardware pretty well, but you need to use VBOs as drawing algorithm which is the only method fast enough. This requires OpenGL 1.5 or later to work.
