Regarding your questions, in the spiritual sky everything is spiritual, so Krsna has no need for living in the heart. They are seeing Krsna face to face always, so what is the use of being in the heart? Outside, inside they are always the same, even their heart that is also sat-cit-ananda. There is no mechanical arrangement like this material body for anyone in the spiritual, what to speak of Krsna.
You can calculate how old is Lord Brahma. It is very difficult to say but only one day of Brahma in which we are, that has not yet passed. We have come in the middle of his first day. We find in Bhagavad-gita that Brahma's one day is equal to 1000 times 400,300 years. So we are fixing his one day, so similarly he has got one night of same duration, such month, such year, similarly such 100 years he will live. He is not even yet one day old, and there are millions of Brahmas and he is one of the smallest.