Auto-updating firmware is only good for however long the company decides to keep updating the firmware. I have an auto-updating router (a Belkin AC 1750) which hasn't had a firmware update in a couple years.

Though I have to say that it's been the most reliable wifi router I've had so far. All other routers I've had before this one would require me physically rebooting them every once in a while, this one has been really stable. Possibly because it has its own "reboot on a regular schedule" feature built-in, so I have it reboot itself daily in the wee hours.