If there’s a lot of the precious blood left over-what do they do with it?

All the precious blood must be consumed after Communion- no matter how much is left (see the Constitution on the Sacred Liturgy #279).
That said, one Eucharistic Minister should not be consuming large quantities of the precious blood as the effects of the wine will inebriate them, so they should drink as much as possible and then ask another Eucharistic Minister to finish what remains.

Julianne Wallace

Julianne E. Wallace is the associate director of faith formation, worship, and ministry at St. Bonaventure University in Western New York. She earned an M.T.S in Word and Worship from the Washington Theological Union in Washington, D.C. and a B.A. in Music Performance from the University of Mary Washington in Virginia. Julianne is passionate about sharing the joy of liturgy with others and helping everyone to worship well.