Bentham gives four qualities of any pleasure or pain (taken singly) as important for purposes of Hedonistic calculation: (1) Intensity, (2) Duration, (3) Certainty, (4) Proximity. If we assume (as above argued) that Intensity must be commensurable with Duration, the influence of the other qualities on the comparative value of pleasures and pains is not difficult to determine: for we are accustomed to estimate the value of chances numerically, and by this method we can tell exactly (in so far as the degree of uncertainty can be exactly determined) how much the doubtfulness of a pleasure detracts from its value: and proximity is a property which it is reasonable to disregard except in so far as it diminishes uncertainty. For my feelings a year hence should be just as important to me as my feelings next minute, if only I could make an equally sure forecast of them. Indeed this equal and impartial concern for all parts of one's conscious life is perhaps the most prominent element in the common notion of the rational---as opposed to the merely impulsive---pursuit of pleasure.

ME Book 2 Chapter 2 Section 1