I get this all the time. It usually hits me that night or at least by the day after. If the high lasts longer, the depression gets worse... I have BP2 also but no one has mentioned rapid cycling to me but I am sure I have it. I can be hypomanic for a day and then go into depression the next day, and I am sure that is rapid cycling. This has been going on lately with me and it really sucks, because now I know even if I have a good day, it will just go away soon anyway and will slump down into depression. It feels like all the happiness gets sucked out of me, and I am left an empty shell. Sorry you are going through this too *hugs if ok*