It got better after sd moved out. Otherwise I would’ve divorced my husband to get her out of the house

I disengaged a year after I moved in with my DH, from his 2 daughters.  They came every other weekend and during Easter, summer and Xmas and along with their vile mother NPD BM, used to make my life a misery for a number of years (try 10+)  DH had a road to Damascus moment in about 2013 and suddenly set some boundaries.  I  may well have left had this not happened.  Anyway, now he seems them every few weeks or so for a meal or coffee, but they hardly ever come to our home any more.  When they do, they are courteous enough to me these days, enforced by him.  

hubby will fly back and forth plus our 2 kids will school in my country. Skids are not a part of my life and i disengaged almost a year ago, its the best decision ever 

Things got better when SD got busier with her own life, but jesus, that didn't happen until she was in her 30s and married. I never saw a grown woman so hung up on spending time with "her daddy." In fact, she probably held on longer because her daddy married and that stoked her sense of competition. 

Things also got better when I convinced my husband to stop paying for SD's luxury items. Yea, I resented both of them slightly less when I finally manged to get him to stop giving her cash.

But the real difference came only when I fully disengaged more than 2 yrs ago. That reduced petty and great arguments with my husband regarding SD -- and she's all we fight about. I told him I was just done with his grown daughter, who didn't seem to be able to regulate her emotions toward me enough to ensure she wouldn't bite every now and then when I see her. I told him I was done with her inconsistent, unstable behavior.

What remains after disengagement is the resentment that I spend lots of days alone while he sees her simply because she is an asshole and he won't call her on it -- it drives me nuts that her bad behavior is rewarded with exactly what she wants: her daddy without a wife.

But I clearly see disengagement is better for me too and absolutely better for my marriage. I finally took the bull by the tail and made a decision about how things would be among the three people in this marriage, and it's been good for me. Now, sometimes, it almost seems like there are only two of us...

Disengaging -does it get better?

I think it depends on why you are disengaging. If it's because of badly behaved kids who are not being parented, it will probably not get better.