I don't remember if it was noted in the anime adaption since it was one of my first shows + it was last October, but the VN shows that the characters themselves find it odd that the next Holy Grail War in Fate/Stay Night started only 10, and not 60, years after the war shown in Fate/Zero.

I removed most of the spoilers (it would only be spoiler material if you hadn't watched Fate/Stay Night) but I left in some content that I feel no one would ever figure out by just watching the animes and have no prior knowledge of the Type-Moon franchise's universes. Like stuff that I didn't even know lol. This is from the Type Moon Wiki:

A cycle of 60 years is needed for the Great Grail to amass enough mana to summon the Servants. The time period between the fourth and fifth wars was the shortest - 10 years.
The participants are 7 Masters and their Servants. It appears as a battle royal that lasts until only one stands, but the real point is to fill the vessel of the Grail with the souls of the Servants. Defeated Servants turn back to being pure energy and should disappear from the timeline they are incarnated into, but the function Grail is to stop that temporarily and collect them
It is suggested that the inconclusive termination of the 4th War -- the great Fuyuki fire-- resulted in the premature occurrence of the subsequent War in Fate/Stay Night. More specifically, the unexpended thaumaturgical energy accumulated through the elimination of Servants was recycled, permitting the Great Grail to reach the required threshold to launch the 5th War a mere decade later.

Which reminds me that we should get one of those "spoiler" tags like some other forums do. Please ZERO? lol :3