Understand the Garbage Collection Interval

I enabled the Page Cache and the “Automatically prime the page cache” for 50 pages every 600 seconds.

By default the “Garbage collection interval” is 3600 seconds, but what happens if I change it to higher value like 86400 (1 day)?

Can I make it higher? When someone posts a comment or when I post/modify an article, those pages are loaded from the cache until they expire?

Please, help me to understand.