According to the CTIA’s semi annual wireless industry survey, in the USA the average length of a local call is2minutes and 3 seconds. It has gone down each year. In 2005 the average length was 3 minutes and 6 seconds. Roaming calls however are stable above 3 minutes and 30 seconds. via textually.org
It is always important to remember how short most mobile calls are, especially when discussing the impact of those calls on worker productivity.