Does dopamine signal become stronger when goal distance is defined using time? Howe et al (2013) found that a dopamine signal becomes stronger as a goal is approached. The experiment involved rats running in a maze. If the rats were close to solving the maze, the dopamine signal became strong. The intensity of this signal did not depend on how fast the rats completed the maze. 

Goal distance was defined in terms of space and distance (i.e. how far a rat was from the end of the maze). Would this dopamine signal also become stronger if the goal distance was defined using time instead? More specifically, if the rats were under some type of time pressure, would their dopamine signals become stronger? 

Source

Mark W. Howe, Patrick L. Tierney, Stefan G. Sandberg, Paul E. M. Phillips, Ann M. Graybiel. Prolonged dopamine signalling in striatum signals proximity and value of distant rewards. Nature, 2013
Hamid et al. Mesolimbic dopamine signals the value of work. Nature Neuroscience 2016.
http://www.nature.com/neuro/journal/v19/n1/full/nn.4173.html

Here is a paper that argues that dopamine signals discounted value of future returns. This is precisely what you are asking. 

the authors argue, that if rewards are further away in time or space, they are discounted, and that DA release in the ventral striatum is more strongly related to this discounted value than prediction errors (current dominant theory of DA function).

I think you should take a moment to read it! It is a seminal paper that makes a profound point about dopamine function, very neatly unifying previously disparate ideas of what the hell is DA good for.