How to cache your membership site
You know what caching is and its benefits, create the page once and serve it many times. The problem with this is that it'll always be the same, and that is not desirable for every page.
Many pages may have dynamic content that'll change for some reason. One of those could be that you show one thing to someone that paid to view more content in a page, while the regular visitor only gets a preview.
And the username would change for each user, of course, so the "Howdy..." message would not be right if the guy gets the page that some other user got cached.
Some have tried partially caching a page, and there are different approaches, but it gets complicated and is generally not recommended.
A better approach would be to cache separate copies of the page, unique for each logged in user. A member would not benefit from the cache someone else caused, but he'd still benefit from it when visiting the same page again.
So the caching plugin would need to know how to cache pages for logged in users in a way that each gets what he's supposed to, and not make a mess.
For my membership sites I use ZenCache, which in the Pro version has the ability to do just that and works great.
You just enable the setting and it'll the do rest for you, very simple to use, and you'll finally be able to benefit from caching for your membership. http://s2member.net/wp-content/uploads/zencache-loggedin-users.png
You can see ZenCache's complete features list here: http://s2member.net/go/zencache
And here's the free version, with a preview of the Pro features: https://wordpress.org/plugins/zencache/
I hope that helps! 🙂