With kids aged 2-10 using these chairs exclusively, both of our chairs were extremely flat within about 3 months of normal use. We just filled them with new styrofoam beads, and I expect they'll flatten again soon and need another fill. I've already ordered the next bag refill, which was $20 and should optimize the fill in each chair. Hopefully at a certain point the chairs with be stuffed full of flattened beads to the point they somewhat hold their shape.