If my partner was having a serious episode at 2am, I would stay up with him until it passed. I know he would do the exact same thing for me. I think it's something that is awesome to do for a loved one going through a rough time.

That being said, some people just aren't up for giving that kind of support. Some people need to sleep at 2am and can't force themselves to stay awake. It can be hard for others to see us struggle, so when the struggle is REALLY BIG it becomes too much to handle, and they withdraw. It sounds like your ex was not able to give you the support you needed. I think that with future relationships it is not an unreasonable request if you are in crisis, but it also wouldn't be unreasonable for the partner to suggest calling a crisis line or go to the hospital.