Sorry OP, I haven't read the full thread, and while I totally agree with you that you shouldn't have to look after your MIL, I do think there are an awful lot of MNetter's who seem to forget that they, in their turn, will get old, and given time, might find that their own kids end up taking this sort of attitude toward them! So please give some thought as to how you would wish to be treated when you get old, and a little scared at how fast moving, and frightening life can seem as the years pass, believe me, you won't all be rushing around and able to do everything that you can do now.
We moved to be nearer to our children and GC about a year ago, after having lived about 250 miles away for quite some time. We're in our 60's, and not in the best of health. However, the reason we moved was not so that we could rely on the family to look after us, but because we were finding it too difficult to care for the large home and garden that we had, and knew that things would only get harder as time went on. The difference is, that we gave a lot of thought to our move, and while we'd have preferred to remain where we were, it was very rural, and not at all practical for when we have to give up driving. We therefore moved to a large village, approximately 30 - 45 minutes drive from family, where there are all the facilities we are likely to need as we get older, but also, so that in an emergency, our family wouldn't be under pressure to drive 5 hours, all the time wondering whether we would still be alive when they got to us.
I guess I've told you this, so that not every adult child automatically assumes that their parents choosing to move nearer to them, means that they expect them to become their carers. In some cases, like ours, the move was aimed at making life easier for ALL of us.