Google's John Mueller said "really large sites" should not use the crawl setting because "setting maximum value is probably too small for what your need." Larger sites need to go beyond that max value in Google Search Console and it is not possible to do that with the crawl setting.
So instead, just let Google figure it out by itself, said John Mueller of Google.
He said this at the 22:01 mark in this week's video hangout "Especially for really large sites, if you use the crawl rate setting, the setting maximum value is probably too small for what your need."
You can access this feature over here and here is the help doc on this topic.
Forum discussion at YouTube.
