Re: how far into the future can monkeys plan to do something?

Hi Matto,
 Thank you for your very interesting question! Humans lead very 
complex lives and need to be able to plan, as you say "what they 
need to do" far ahead. Monkeys live relatively simpler lives, but we 
know that they are also able to plan "what they need to do", at least a 
little!
 The main activity in the monkey’s life is to find food and two studies 
have shown that monkeys can use planning to find the most food 
with the least effort. In both these studies (Menzel, 1973; Cramer and 
Gallistel, 1997), the researchers took the monkeys with them and hid 
food in many (18 or 25) small holes in the ground. During that part, 
the researcher and the monkey walked "the long way around" from 
hole to hole, sometimes going to a very far hole before coming back 
to a closer hole.
 After all the food was hidden, the monkey was released and it was 
now free to go find the food that had been placed in the holes. 
Instead of simply retracing the sequence in which the food had been 
hidden, the monkey showed no hesitation in picking a much shorter 
route to find the food! This means that he had memorised the 
locations, and then planned the fastest and easiest way to get the 
food! This shows that monkeys can plan ahead at least for several 
minutes.
 Vervet monkeys, which are relatively small and have relatively small 
brains, could find a quick route to find food in six holes. 
Chimpanzees, which are very similar to man, were much better and 
they could find the shortest way to retrieve food from all 18 locations. 
It is very possible that they could plan much longer ahead, hours or 
maybe even days if the situation required it.    
 I hope this answers your question.
 Cheers
  Benoit

References:
Cramer, A.E. & Gallistel, C.R. (1997). Nature, 387(6632), 464.
Menzel, E (1973). Science, 182, 943-945