alwaysthere,
There are no stages, only symptoms of depression, hypomainia, and mania. The episodes take their name from the mood state occurring at that time.
One little fight or argument is not going to trigger and episode. If you are feeling responsible, stop. It is also not your responsibilty to remedy the situation or take care of him and his illness. Obviously you care and feel like you are always there for him but you must ask, when is he going to take care of himself, if you are always there to take care of him.
He is the one that is in a positioin to be most aware of symptoms and take action to get the appropriate treatment. If he does not learn to identify his symptoms and act quickly then he will continue to go through episodes of longer duration because of his inaction. You cannot do all of this for him. If he does not mind the episodes or what results from them, then he can continue to do nothing. If he does not like the instability, then he must do something to change the situation.
You can research, you can learn, you can even seek counseling to help you cope with issues related to him and his disorder but none of this is going to help him if he is unwilling to help himself or listen to you.
If he is on medications and continues to have episodes, then he needs to see his psychiatrist and have him evaluate his treatment and make the appropriate changes or adjustments to his medication. He needs to identify when their may be an issue with his medication. He needs to make the choice to seek or to go into his therapist if their are issues that are challenging him. You may be able to help him but he is the one closest to the action and in a position to recognize and react appropriatly.
You can do only so much and must accept your limitations. You can help him save himself but you are not and cannot be his savior. Do not feel bad or frustrated when your efforts are not successful. You are doing your best and must recognize and accept it as good enough.
If he suicidal ideation increases to planning or putting the plan together and there is a sign of serious intent, contact the authorities immediatly, so he can be evaluated and possibly treated. If he is not willing to help himself and will not listen to you, then he will have to listen to them.