Office 365 IP Address changes

Hello,

In order to allow Office365 Exchange IPs in a firewall, i'd like to use Microsoft's API stated in this page:
https://docs.microsoft.com/en-us/microsoft-365/enterprise/microsoft-365-ip-web-service?view=o365-worldwide

Specifically using id 9 and 10.

My questions are:

1. Is this page/API mentioned in it(https://endpoints.office.com/endpoints/worldwide?clientrequestid=b10c5ed1-bad1-445f-b386-b919946339a7) consistent?

2. Are there pre-defined periods of time that these IPs/CIDRs change?

For example, if Microsoft will decide to add/remove an IP/IP range from mentioned above URL, can I be sure that there will not be a gap of time since the actual IP change and an update of that page?

Thank you in advance.