What router does he have now? How many people are on it at a time? You shouldn't get booted off because of the number of people using it. I have at least 12 devices in my house connected to our router. Often we have four or more connected at the same time. When someone gets booted off, it is an adapter problem in their device, or the laptop has gone into sleep mode, and has lost the connection.
Getting "booted" off is probably a connection problem with your wireless adapter. Could be the distance you are from the router.
A dual band wireless router is only a benefit if you have a wireless adapter which uses the 5 GHz band. Most "off the shelf" laptops and desktops don't use this band. My smartphone uses this band, but none of my laptops do.
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