I used to think that Ennis was pulling away from Jack a bit, but then the reality of life set in. Ennis truly did have to work to earn his keep, especially with the whole child support thing and not having a second income (Alma's) to help him out. Also, cause he's getting older maybe it's harder to get jobs and randomly taking weeks off every few months would probably not fly with his employers at all.
And yeah, Ennis waited till the end of the trip so Jack wouldn't sulk the whole time and ruin the precious week they had together