A good TA will be able to get you at least 5% below what CruisePlanner posted. TA consortiums can also get you special excursions or shipboard credit in addition to the 5% discount.
In 14 years of sailing Regent, I have never seen a "flash sale" but I have seen many specials that do show up.
"Carpe diem quam minimum credula postero"
Seven Seas Explorer - Miami - Venice - Mar 2017
Silverseas Explorer - Arctic - Aug 2017
Seven Seas Voyager - Rome to Beijing - Oct 2017
Seven Seas Mariner - Lima to Buenos Aires - Jan 2018
Silverseas Explorer - Siberia - Jul 2018
Seven Seas Mariner - Australia Circumnavigation - Dec 2018