> If both max-age and an Expires header are set, max-age will be used by Cloudflare.
If both max-age and an Expires header are set, max-age will be used by Cloudflare.

s-maxage= in it's responses?s-maxage= from the origin, but without actually touching your origin?
s-maxage= to 1y (in seconds) from your origin).

s-maxage=600" to Cloudflare.s-maxage=600", however, that isn't necessary - unless you have something in front of Cloudflare (e.g. another CDN), that needs to see it.