AVSET is supposed to reduce volume scan time, but I'm not sure of it's status.
http://www.roc.noaa.gov/wsr88d/NNOW/AVSET.aspx
http://www.roc.noaa.gov/wsr88d/NewRadarTechnology/NewTechDefault.aspx
From the AMS Radar Conference paper listed there:
"The basic premise of AVSET is to terminate the current volume scan after the radar has scanned all of the elevations with operationally important returns. In other words, once the data collection elevation overshoots the significant radar returns, the volume scan is terminated because there is no operational benefit realized by continuing the execution of the current volume scan, and a new volume scan is begun. The net effect of AVSET is to shorten the elapsed time between data collection on low elevation angles during periods when no significant data are available on the higher elevation tilts."