It's been said many times... depends on the flavors. If you're changing types of custards, no biggie. Some flavors will actually complement each other as the flavor changes. I did, however, have problems getting one flavor out. Put Suicide Bunny's Madrina in my Subtank. After rinsing out and re-wicking, I could still taste it. Finally had to soak the o-rings in rubbing alcohol to get that taste out. It even came through my strong menthol and would NOT go away.