I was just wondering what is the earliest age toddlers drop their day sleep completely?

DS is 15 months. He dropped to one day sleep around 13 months, and would usually sleep for 1.5 hours. However, in the past few weeks his day sleeps have been getting shorter and shorter. Now I'm lucky to get 1.5 hours out of him, usually it's just on an hour. Today it was 45 minutes! I try and resettle him when he wakes this soon, but he simply doesn't want to go back to sleep.

Going by this I'm thinking DS will probably drop his day sleep at a fairly early age. Just wondering how long I've got, lol.