https://cabforum.org/2025/04/11/ballot-sc081v3-introduce-sch...
You cannot issue a publicly trusted TLS certificate with an empty expiry, or an expiry date more than 200 days away (as of March). If you want to talk about private CA, then the certs can follow all sorts of rules.. they don't even have to be about TLS.. they can be for SSH at that point.
You can create your own without the use of cloudflare.. you can set it to a 100y expiry if you feel like it.