Keep your site consistent and by using the sort order feature of Shopify Power Tools, which allows you to specify a sort order for your custom and smart collections.

Simply select the sort order you would like to enforce for you custom and smarter collections.

Simply select the sort order you would like to enforce for you smart collections.

This will update every time your store update is run, usually every couple of hours.

If you want to disable this feature set it to No Default Sort Order