Is there anything significant about when Lennie asks George to talk about the dream?Why do you think he picks those times to ask? What has triggered him off? Has George said something?
George's recounting of the dream has a calming effect on Lennie. He appears to request it when he is in need of comfort and/or a positive focus.
We see him request that George tell him the dream as they sit by the campfire in the way to the ranch. Lennie knows each detail, but is soothed by George’s rendition-
“You got it by heart. You can do it yourself.”
“No, you. I forget some a’ the things. Tell about how it’s gonna be.”
Lennie is disturbed by change and, although he cannot fully recollect the events in Weed, he is aware that the new ranch may be a challenge. He relies on the stability which George provides and the dream denotes this.
George also recalls the dream to Lennie and then Candy when the men are in the bunkhouse, Candy has lost his dog and has no future. Curley and his wife present real dangers to George and Lennie and for each of them their days at the ranch are numbered. The dream here provides a diversion and a vestige of hope - something they all need at this point in the story.
The final time that George relays the dream for Lennie is just before George shoots him. This will be the biggest transition of all for Lennie, and George tries to make Lennie’s passing as comfortable as possible. It is the end of the dream for George, but could be a step closer for Lennie.