Offering the time is a 2 edged sword. Good for you to get some time to get things together. Bad because it is changing the expectations of the custody agreement and XW will demand more of these exceptions and guilt you about doing it this time.
"... well you gave them to me last year, why not this year?..." blah, blah, blah
But he can simply say something along the lines of, "I know, I think it's wonderful the boys got to enjoy some extra time with you. But we are sticking to the plan in the meantime." This woman will find ANY reason to provoke an argument, Jim needs only to control his reactivity and not rise to the bait. He cannot live his life around this capricious woman's moods. He can give himself a bit of a holiday now though and catch up on some house stuff and relax.
M 10yrs T 13yrs BD #1Oct 2015-PA between WAH and COW BD #2 April 2016-WH resumed PA, she broke it off Jan 2 2017 WH says he wants divorce April '17-Letting go 2018 D busted DD8, DS6, DS3