Power point 2010?

Am creating a 2010 PP Show, accompanied by 2.5 mins of sound, showing my Art and Design Portfolio in search of employment. Potential Employers will view without my presence. I don’t want pics/slides of my work to linger too long and I don’t want the pics/slides to advance too quickly. Does anyone know the approximate average timing comfortable for a viewer ? My current guess is 7 secs for each image…some of which include a few typewritten descriptive words,{ murals, props, recognizable client names, etc… }. Your advice shall be greatly appreciated !