Aidyn began dropping his day sleep a couple of months after turning 3. However the problem was then that he would fall asleep at around 5 or 6 pm (just on the beanbag or living room floor) and then because of this short nap he wouldn't go down properly at bedtime and would want to stay up till all hours!
So we had to endeavour to either get him to have an earlier sleep, or to make sure he didn't crash out somewhere before bedtime.

Now that he is over 3.5 he has definitely outgrown his need for a nap, and lasts ok until bedtime each night. Although he does tend to get very tired still around 4pm I find.