Although water can be reused almost infinitely, any one drop may go through a long process before it is available again.
It might sink into the ground and remain there for half a century. Or the drop might freeze into a snowflake and fall on a glacier in the Alps, where it could stay for thousands of years.
On the other hand, water that evaporated yesterday over the Pacific Ocean might become tomorrow’s storm. A drop might fall right back into the ocean and evaporate again the following day.