What is cache lifespan?

WordPress uses nonces as security tokens which are printed in the source code of the page. These nonces cannot be reused and are valid for 12 hours by default, but developers can change that value. The nonce getting invalidated can affect all kinds of functionality on the site like form validation or the visual appearance of a page among others.

Setting a cache lifespan to under 10 hours ensures the cache is flushed automatically once the nonce expires. This way you can use WPO cache on sites which use nonces.

The cache lifespan option is set to 10 hours by default, but you may have go down to 8 or even less. A lower cache lifespan value will result in more frequent cache update activity on your server, and thus more preload processes, if activated. If you notice any issues due to high server load, set a higher interval for the preloader.