Those are the conversations that are familiar to me with my W, regarding the kids' schedules...
I can't say that mentioning my concerns about being "first option" for the kids helped or had no affect...
In the moment, my W will get flustered and I can tell she's working things through her foggy mind and then she'll say something that seems to indicate that she'll make more effort... and then doesn't seem to...
Anyhow, just posting to let you know that I've been there...
It's one of the reasons that I'm going to dim... in order to have a little more communication with my W and have more opportunity to talk to my W about the kids' schedules so that I know when I can jump in and say "I'd like the kids on that day that you are away or working late"... or similar...