I make the kefir for 24 hours like you. Then I put a couple of cups on a piece of cotton in a small measuring jug. Tie up with string and to a wooden spoon and suspend over a glass jar. The whey drips out and 24 hours later I have made cream cheese and whey. So it's had 48 hours altogether.
If I make cream it's for less time ie 12 hours later so 36 altogether. Slightly less whey obviously.