(CNN) - We have just officially learned that President Obama will speak for some 70-75 minutes tonight. Conventional wisdom holds that speeches should be short, to the point and leave people wanting more. Is this a good idea for the president tonight? Bill Clinton could pull it off, as he did. Barack Obama is an excellent speaker, as we all know, but can he pull it off, too? A big challenge - and we will all stay glued to watch, or will we?