Factory reset means my custom firmware will be gone too? Uptime no issue, mine is still on without restarting my router.

Someone can start a "Router recommendation" topic here and get a mod to pin it so that it is always at the top.

Send back to RMa work? I just bricked mine too. Afraid they don't allow for warranty claim

Yesterday tried to flash to Advance Tomato firmware but failed miserably.

At the moment, i am at xwrt firmware and try to upload tomato firmware via the web interface.

Before start to flash, I perform the following :

Backup current setting
Restore factory setting
Lastly is to upload the tomato firmware.
Flashing show successful and ask to reboot.

Turn off the power and then turn on back , wait for the router to boot up.

All lights turn on and seems normal.
Able to ping the gateway 192.168.1.1

However, when try to open the weblogin page 192.168.1.1 , the page cannot be display. Wait for 10 mins also same result.

Telnet to port 80 not able to connect .

Lastly need to reset the modem , goto CFE Emergency Boot page  to load back XWRT firmware

Anything that I miss during flash the firmware ?

It's not just about stability, you also need to think about security
In some, if not all of the updates, ASUS or Merlin release a security fix that will close a loophole / backdoor preventing from someone hacking into your network & every device connected to it
Haywire how? Care to explain?

What kind of problems? So far my WS880 is rock solid be it wifi or wired..

When the issue happens, does it affect all your wireless devices or only a few?

Stock firmware? If it is, yes, I'm having the same issue as yours.

Once in a while, the wireless is connected, but no connection. Have to switch on and off the wireless on my devices (not the router), then reconnect and the connection is back. Wired Lan is fine all the time, just the wireless has such issue. 

Do you know what is the temperatures of CPU and wifi are running?
Maybe it is too hot??

Maybe worthwhile to set schedule for the wifi to shutdown for 5-10mins every night, possibility this will solve your issue here.

I don't think, this can't be firmware related.
It happen to me once before on 2.4ghz wifi on my WS880 with 380.64 after months nvm restart the router. I still don't why it happen, but after i set schedule, I didn't see this issue till now.
Unrelated here, yesterday I also put a small cooling fan behind the router and it able to cool the CPU temperature from 70degc to 60degc, 5ghz wifi from 53 to 49degc and 2.4ghz from 50 to 46DegC.
I think this will improve the long term stability of the router.

At maximum, how many devices is connected at once?
Also, since you also mentioned that you've never tinker with the wireless settings, how about changing some now?

My WS880 just turned off both the wireless by itself
I'm the only one using the internet as I stay alone in my house and no one hacked into it
Checked the system log, definitely no one hacked my system

So weird

Anyone successfully use usb tethering directly to the router?
I just tested it, switched to android phone on the usb device
But is still not connected?
I'm on Firmware 380.65 btw

Power adapter failure, can claim warranty? Or can be replace by higher ampere output power adapter?

What is your reason for not using the stock adapter?

Are there any WS880 owners using it for Maxis Fibre or TIME Fibre?

Just curious.