I reckon it really really varies. Between children, between families, and depends on stages too.

Olivia cut her day sleeps at about 3, but still has an hour "rest time" in her room.

Charlie stopped sleeping at about 2.5 years old, but now has reverted (at just over three) & will have a nap most days.

But other kids I know cut them all together at as little as 12 months!