If your milk is raw, it won't really go off. It will just sour and separate into curds and whey.
My DH forgot to bring the milk in from milking one morning and I found it sitting out in the garage later that afternoon. So I just left it sit on the kitchen counter for 4 days until it was completely separated, and turned the curds into cheesecake, and used the whey to make baby formula. It was a real challenge to not see it as "off" but as a nutritious food!
Anyway - I think 24 - 36 hours is enough for kefir. Mine only thickens to a runny yoghurt consistency. I think the one you made sounds perfect.