SOLDATOOFF/Shutterstock No Wi-Fi router lasts forever. Even if your current unit functions reliably now, you'll eventually need to upgrade to a new router to ensure optimal performance. Checking for certain features when selecting a replacement can help you find the right model for your needs. For instance, if security is a priority for you, look for a router that offers the option of setting up a guest Wi-Fi network. A guest network is exactly what it sounds like: a separate network that visitors can use in your home without connecting to your main network (which would require sharing your password). If a router offers this feature, the same unit that provides your usual Wi-Fi network can provide this network to guests. Choosing a router with this option doesn't just boost security — it can also limit how much of your network's bandwidth a guest uses. Although most routers these days typically offer this feature, it's still worth confirming a given model does before spending your money on it.…