How often should we refresh the list of allowed cloudflare IPs?

This explains that you can allow the cloudflare IPs to pull from the origin but this list changes over time right? How should we keep these IPs up to date?

I can’t remember the last time that list has changed. Years, it seems. So it’s up to you how often you want to check.

If I checked every year would that be fine? When cloudflare adds an IP address is it ok if requests from those IPs fail for 12 months?