Many people seem to have issues with 5ghz but that works great for me. I "think" my problems are with 2.4Ghz. With the latest stock firmware it seemed worse (2-3 days and it completely locks up, even the lan connections). Using Merlin's latest release, (6-8 days before complete lockup).
Most of my usage is on the 2.4ghz side with 4-6 devices connected at all times. On 5ghz there are only 2 devices and they are mostly turned off or in sleep mode.
Currently I have 2.4ghz disabled and I'm using an RT-N16 with hggomes firmware hooked up as an AP for 2.4Ghz. Hopefully this will shed some light on where my problem is. My up time was 5 days but recently i noticed that it rebooted itself 17 hours ago. The last entry in the log before it rebooted had to do with my wireless canon printer that uses 2.4ghz.
I'm still trying to wrap my head around this problem.
EDIT: After more testing it does seem to be the 5ghz Quantenna radio. I'm starting to think they cant fix this thing with updates.