What an interesting question! Variations of the word “stretch” are used exactly nine times in the course of the novel. Interestingly enough, the word is often found a few times in some important places (even though most don’t have much to do with time, per se). The fourth and the ninth instances are the one to concentrate upon in regards to time.
In the fourth instance, Nick comments about becoming thirty. “’I just remembered that today's my birthday.’ I was thirty. Before me stretched the portentous menacing road of a new decade.” Nick, now caught in the world of the West Egg rich, feels the ominous pressure of a new decade of life, one where he will be pressured to make himself more of a success as a “bond man.” This is also evokes a bit of sadness for the reader. Birthdays, of course, are usually celebrated with flourish in our society. In Nick’s new world, no one really cares. Even worse, Nick states it as if he knows that no one cares. No wonder he flees back to the West.
In the final instance, and by far the most important one, Nick ends the novel on a note about time.
Gatsby believed in the green light, the orgastic future that year by year recedes before us. It eluded us then, but that's no matter--tomorrow we will run faster, stretch out our arms farther. . . . And one fine morning---- So we beat on, boats against the current, borne back ceaselessly into the past.
Note the use of the word “stretch” here. Time doesn’t matter, it will keep going on and on … we will simply “stretch out our arms farther,” trying a little harder to reach our unreachable dreams. Ironic, though how we are not brought into the future but “into the past”! How well that fits with Gatsby’s previous comments!
Just as a final note, the other instances of the word “stretch” really aren’t as important in regards to time. One other instance that’s really important is the first instance where we first see Gatsby as “he stretched out his arms toward the dark water in a curious way” towards Daisy’s green light. Another important instance, dangerously close to Gatsby’s death, involves Gatsby when “he stretched out his hand desperately as if to snatch only a wisp of air.” It’s part of a flashback when Gatsby mourns his return to Daisy’s hometown, … while she’s on her honeymoon with Tom. The other instances are really just simple details of setting and not worth noting here.