In general SOHO (Small Office Home Office) routers tend to lose signal strength over time. The transmitter components wear out. Normally it's caused by the cheap electrolytic capacitors the manufacturer used. It's the same issue every amplifier and radio built in the last 30 years has had. There are lots of articles on the web about people replacing all the caps to "fix" their router.
Sometimes the flow solder systems do a bad job of affixing the chips so they start to fail with heat and dust over time. You can maybe fix this by taking the board out of the router and baking it at 500 to 600 degrees but not always and you may destroy the board in the process.
The average lifespan of a SOHO router is only 2 years or so.
I have a Netgear wireless router (can't remember the model right now) that supports 802.11n and it does work well. Not all devices support every 802.11n connection even if they say they do. All 6 cell phones in my house say they support N but only half them work when connected the N network. Sometimes laptops say they have a chip that supports N but the manufacturer chose to not install the chip and antenna that makes it work (I have two of these) from Acer and the label on the top stating it has 802.11n support.
As for the Genie app? Ya, it makes setting up the router easy but Netgear requires you sign in on an external site to configure the 802.11 network with a different user ID and Password than you use to login on the router locally. That's kind of a PITA to me. On top of that, when all the browsers disabled Adobe Flash for security reasons, you could no longer connect to the external site and configure the 802.11N connection. Flash is a POS and full of security holes but to maintain your network, Netgear makes you use it. Sorry, kind of a raw nerve.
Maybe all the routers I've had in the last 8 years were too cheap to be expected to work well and last but it's been a long time since that first Lynksys router lasted for 9 years with no issues.
Oh well, I hope the NightHawk works well and for a long time for you. Let us know if you start to see any issues creeping up.