I'm upgrading a small site currently in Drupal 6 to Drupal 8, it's for a non-profit and doesn't receive all that much traffic. It's a relatively static site, content will be added regularly, but certainly not every day. While the amount of traffic is easily handled even on shared hosting, I'd like to keep the page loading times low. I used Boost for that on Drupal 6, but now with Drupal 8 I want to use the internal page cache.
From what I understand, Drupal 8 should be able to automatically invalidate the cache when nodes are edited. So what I'd like to do is to cache all pages of my site indefinitely until the data behind them actually changed. But the cache dialog on the performance admin page only allows a page cache maximum age of 1 day.
Is there a way to configure a stock Drupal 8 to cache pages forever? The cache should only be invalidated if nodes are edited and the page actually changes content. Ideally I'd like to automatically pre-warm the cache as well.