So what exactly is the problem with it taking its "sweet time"? Isn't that just a way of saying it will wait until it actually needs the memory to drop the cach

So what exactly is the problem with it taking its "sweet time"? Isn't that just a way of saying it will wait until it actually needs the memory to drop the cache? Perhaps if there was a significant performance hit incurred when dropping caches you may want to do it more eagerly.. but is there?