For people who have Bipolar disorder the "crash" from a manic or hypomanic state is sudden it can happen over night. The Major depressive episodes have a much more gradual onset and offset. After the hypomanic or manic episode he may have a normal episode or he may fall into a major depressive episode. Have you seen him really depressed for a long time like a month or more? he may not be bipolar but he may have cylcothamia. Cylcothamia can be kind of thought as bipolar lite. Cylcothamia is marked by a person having at least one dysthamic period and at least one hypomanic period.... Also hypomanic and manic episodes really don't last all that long compared to depressive episodes. How long has your husband been in a hypomanic episode?

Hope this helps some,
Jason