Almost six years now. I still have the old silver DSPhat from when they first came out. After years of dropping it on the floor, down stairs, dropping stuff on it, and spilling stuff on it, it works perfectly fine pretty well.
I can't close it anymore or else the game will most likely freeze within 10mins. The paint is also beginning to chip off. The touchscreen will occasionally malfunction and detect everywhere I tap as if I touched on the far right on that spot. It can fix during gameplay or if I leave the DS alone for a few hours to days with no card in.