Some of my systems I use less frequently, I update about once a month. Never had any major issues. Of course, the longer you wait between updates, the higher the chance that the update will require a manual intervention.
Even if you update less frequently than that, there won’t be any issues with system stability because of that. Your system will not just break on its own even if you completely stop updating it. At some point, there won’t be any mirrors serving you old packages. Also updating after a very long time could be quite a chore.
But theoretically, you could have an offline computer running Arch Linux which you never update, and never install anything new on it, and it will run perfectly indefinitely.
A much bigger issue with updating less frequently is not getting any security fixes. There are critical vulnerabilities in your browser just waiting to be discovered and abused, so you want to get those updates as soon as possible. This is true for fixed release distros just as much as it is true for rolling release distros, the difference here is that you always use the latest version of all packages after you update. There is no separation between feature updates and security updates.
So my advice is: update whenever you have the time to do the update, and fix eventual issues that seldom arise from updating. Pick the most convenient time. Don’t update your work computer hours before an important deadline, but also don’t wait too long between updates so that you run software with known security vulnerabilities.