We have definitely bought 95% of our 3-year-old's clothes through Mom-2-Mom and other used sales, and seasonality is an issue. (we are on the other end of the scale--is is above the 99th percentile in height, but super skinny!) If you think you will be borderline, buy some things on either side of the border. at $1 apiece, you can afford to be 2,000% wrong vs. buying new things because you didn't want to take the chance. And, if you are so inclined, you can always cycle the clothes back into the system anyway, essentially making them free or very low rent, if you account for some losses due to wear or staining.