From where you entered into the park till you get to Base Camp or Plaza de Mulas as it is usually known usually takes two days.

As you trek you will see the flora change around you as you gain altitude.  Expeditions usually trek for about four hours to an area called Confluencia.

See the above map of the area.

Here you will spend a night to acclimatize.  The next day is a short day of trekking to Base Camp.  And believe me, what a great site to see!