Dear Paul:

Sorry for the delay in answering.

Well, I think you have summarized the question of the significance of the practice of drinking blood. It is because there is life in the blood. The ancient pagan peoples had an intuition about the significance of blood and sacrifice because God tells us that all peoples have a basic knowledge of Him. We inherit this knowledge, as it were.

But, since these ancient peoples did not have the Revelation of God given to the Jews first, and then to Christians, all they could do with this intuitive knowledge is to interpret as best they could -- thus, the shedding of blood in sacrifices and drinking that blood and sometimes eating the flesh. There were all sorts of interpretations for this practice including, it was thought, to prevent their enemies from favor with a deity, to gain knowledge and life through their enemies, and a host of other notions.

But, the fundamantal idea of sacrifice, eating flesh, and drinking blood buried deep in their souls comes from God. All such practices actually look forward, in a very imperfect way, and often evil ways, to the pure sacrifice of Christ and the eating the flesh of our Lord and the drinking of His blood in order to have eternal life.

As for how long a person is with a person who drinks the person's blood, the belief on that will vary from culture to culture.

We know that for the Eucharist our Lord is with us only until the Eucharist is dissolved. If we allow the Eucharist to dissolve in our mouths, as some people do, then the Lord is with us only for a minute or two. If we swallow the Eucharist whole, or munch on the Eucharist as the Scriptures mention, then the Lord is with us for up to around fifteen minutes.

This economy of material presence also is true for blessed objects, such as a blessed rosary. If the rosary falls apart and no longer resembles a rosary, then the blessing ceases. The same goes with a cursed object.

Thus, since this is the economy of such things, I would say that any presence of a person still in the blood or flesh is certainly no longer there once the blood or flesh is dissolved by stomach acids -- that process takes around fifteen minutes or so.

This is one of many reasons we receive the Eucharist not once, but many times.

Since the blood and flesh represent life, by God's design, receiving our Lord's blood and flesh brings actual eternal life. As manna gave life to the Jews in the desert, so Christ's flesh and blood, as the manna of life, gives us eternal life (John 6:30ff)

I do not know if this is what you are looking for, but these are my thoughts.

God Bless,
Bro. Ignatius Mary