I don't think I had any expectations of my MIL, well either of them as I have been married twice. My first MIL was pleasant but after ten year I felt I hardly knew her, she was very dominated by FIL and was a very quiet person but pleasant. My 2nd MIL was very difficult, my DH went no contact with her more than once and I worked hard to keep the relationship going. I don't think I ever got any thanks for it. I think she didn't like the fact I'd been married before and had children.
I have 3 sons with partners but not all married, I still view each as a DIL. One is very easy to get on with, one can be a bit tricky and one would prefer my son had sprung into the world the day they met and had no family or friends from before her. I have a friendly relationship with all of them, could bang two heads together at times as they make it hard for 2 of my sons to maintain their relationship. They are all good mothers from what I see and my sons seem happy so it is fine from my perspective. I don't expect them to do the family stuff, I always contact my sons rather than their partners, generally the only time we have contact direct is when they are sending me photos of the GC on Whatsapp or I am asking for ideas for presents if son hasn't got back to me or I thank them for Christmas/birthday presents . I do find my SIL easier.