That presumably depends on when the caching was put in place.
If the number was in the thousands in the late-90s, you could probably get through all of the sites.
If the caching was put in later, say, the early 2000s when google started getting really big, the number might just keep growing until it eventually looks ridiculous.
I've never worked at google, but I've seen a few systems that broke in weirder ways when nobody bothered to maintain them after they had outlived their usefulness.
If the number was in the thousands in the late-90s, you could probably get through all of the sites.
If the caching was put in later, say, the early 2000s when google started getting really big, the number might just keep growing until it eventually looks ridiculous.
I've never worked at google, but I've seen a few systems that broke in weirder ways when nobody bothered to maintain them after they had outlived their usefulness.