Great! Let me know if you see anything out of the ordinary, or any functionality you’d like and I’d be happy to see what I can do!
The 10 minute config has existed for a long time from when the logic was that if there were any issues with cache not being purged, then it would kind of organically purge. I don’t think it’s too big of an issue anymore, hence why I made this plugin. I am hopeful that a change goes through as the WP Engine platform evolves that optimizes the cache further, but I know there is a lot of stuff coming up that should make it matter less.
The only disadvantage would be content that is updated but not associated with something that WP Engine purges automatically, then it wouldn’t update on the page. I haven’t seen anything like this in my testing, so I wouldn’t be too worried. If you’re not seeing any weird things with cache at 10 minutes, you probably won’t see it at a longer time.
They are not, last-modified is something I built in specific to the plugin. It is really only leveraged by the browser currently, but I am hopeful that it’ll be more useful soon with maybe varnish or a front end CDN system.