I used to have this issue with both my siblings when they visited. Since we live 4 hours apart it's hard to set exact times due to traffic. Prior to cell phones it was a huge issue, now not so much. I just go about my day and they can call me when they're getting close. It used to really steam me because they'd say "I'll be there around dinner time" and show up at 10pm when I was getting tired and ready for bed. Between the cell phones, the fact that they both married people more like me, and them no longer wanting to drive after dark (we're old and they're both older than me, LOL!) it's not an issue any more. I also learned to give up on expecting them when they said.
I always have things timed pretty close and call and give as much notice as I can if I'm not going to meet the preset plans. I consider that the respectful thing to do.
