How to Change DHCP Lease Time - Nighthawk XR500

I've been having this issue as well. You'll be somewhat relieved for me to inform you that its not the router lease time affecting you. In fact, your router is not the root cause if your dropped connections.

If your connection is dropping for a couple seconds or less than a minute or so, then whats really happening is you ISP communication is having difficulty transmitting the signal to you. You're pretty much right on the threshold of a reachable signal. Although you may be on the threshold, a typical transmit level tends to fluctuate up and down due to one or many different factors... traffic utilization in your area could be one issue, or even the time of day when it gets hot or cold as the center conductor expands and retracts within the coax cable that your ISP is being transmitted from, assumes that you're not on fiber. Google T3-T4 timeout, you'll see a lot of your issues relate to these terms, which indicates that your ISP transit levels are too low and you need to call them out to your house and get crackin. Make sure you mention T3 and T4 timeouts, they'll know what it means.