How do I decide exactly when to add a switch?

List current wired devices and what you expect to add over the next 12–24 months, noting which need fixed connections and whether you want separate VLANs or PoE for certain devices. Add a growth margin of about 20–30% to that total so you’re not forced into a quick upgrade. If you’re near the router’s port limit or you need features like PoE, VLAN separation or better local-device management, plan for a switch now. A common path is router with spare ports plus a compact managed switch for growth, or a higher-port model that covers future needs; Comset can help map your device list to a port plan and advise whether a switch is worth adding now.