Yes, regular maintenance is necessary to ensure your DIY window box stays in optimal condition. For wood, it should be treated periodically with a sealer or preservative to prevent weathering and water damage. Metal boxes should be checked for corrosion and repainted if needed. You should also make sure there are no loose screws or connections that need tightening. It's a good idea to inspect the window box once every 6-12 months for any signs of damage or deterioration. Additionally, the plants inside should be checked frequently to ensure they're healthy and have enough water and nutrients.