Cache-Control headers repeated; valid or not? (Nginx)

Yes, it's valid and equivalent to use multiple Cache-Control headers.

From the HTTP 1.1 spec:

Multiple message-header fields with the same field-name MAY be present in a message if and only if the entire field-value for that header field is defined as a comma-separated list [i.e., #(values)]. It MUST be possible to combine the multiple header fields into one "field-name: field-value" pair, without changing the semantics of the message, by appending each subsequent field-value to the first, each separated by a comma.

It's easy to verify that this provision applies to the Cache-Control header because of how it's defined:

Cache-Control = "Cache-Control" ":" 1#cache-directive

To understand how to interpret the line above, see the spec's notational conventions. The 1# means "a comma-separated list of one or more".

I was having the same problem on different configuration.This is what currently works for me.

Example taken from Module ngx_http_headers_module

map $sent_http_content_type $expires {    default                    off;    text/html                  epoch;    text/css                   max;    application/javascript     max;    application/octet-stream   max;    ~image/                    max;}server {        expires $expires;        ....}