As SB said, most Communions are held in the spring. FFC moved it to December so he could make a speedy transition for Michael--to Miami, then NY, then Havana to ring in the New Year, all in a matter of (probably) no more than two weeks. Evidently Michael had a lot of clout with the Church--and that was before he got pally with Archbishop Gilday and bailed out the Vatican Bank! Also, he had his own family priest, Father Carmello (just like medieval and renaissance royalty).

As for Mama: Michael returned to Tahoe probably right after he met with Tom, Rocco and Neri in Vegas following his swift exit from Havana. Mama looked healthy enough, but she could have been a heart attack waiting to happen. And, we don't know how much time passed from that scene until her death.