Well, let’s see. We can see from early Christian inscriptions that they believed in the intercession of the saints in heaven. You have things like:
“Let us remember one another in concord and unanimity. Let us on both sides [of death] always pray for one another. Let us relieve burdens and afflictions by mutual love, that if one of us, by the swiftness of divine condescension, shall go hence first, our love may continue in the presence of the Lord, and our prayers for our brethren and sisters not cease in the presence of the Father’s mercy” (Cyprian of Carthage - Letters 56[60]:5 [A.D. 253]).
“Atticus, sleep in peace, secure in your safety, and pray anxiously for our sins” (funerary inscription near St. Sabina’s in Rome [A.D. 300]).
and
“Pray for your parents, Matronata Matrona. She lived one year, fifty-two days” (funerary inscription near St. Sabina’s in Rome [A.D. 300])
and
“Mother of God, [listen to] my petitions; do not disregard us in adversity, but rescue us from danger” (Rylands Papyrus 3 [A.D. 350]).
So, those were examples of how early Christians believed in the intercession of the saints, pre-dating the finalization of the Biblical canon.
Looking at the Biblical canon itself-- you have the very famous quote from James about “the prayers of a righteous man availeth much”. Who is more righteous than the people who are in God’s presence in heaven? If you look at Revelation, it says–
8 And when he had taken it, the four living creatures and the twenty-four elders fell down before the Lamb. Each one had a harp and they were holding golden bowls full of incense, which are the prayers of God’s people.
What are they doing with the prayers of God’s people? Are they praying with people? Are they praying for people? Are they doing both?
You have the entire episode of the Wedding at Cana. Mary says to Jesus, “They have no wine”, and he says, “What is it to us? My time hasn’t come yet.” And she says, “Do whatever he tells you.” And he performs the miracle-- because Mary always aligns herself with God’s will. But would the miracle have been performed in the absence of her intercession?
We’re supposed to pray for each other-- the Bible is full of countless verses about praying for each other. And God is the God of the living, not the dead. So is death sufficient to separate people enough so that they say, “Well, I’m done here. You guys can keep on doing what you’re doing. I’m off to heaven. You can tell me what I missed when you catch up.”

Or is the Body of Christ still the Body of Christ, regardless of where its members happen to exist, either inside of time or inside of eternity?