You guys should check out a book called "Songwriters on songwriting" by Paul Zollo. Many interviews with many songwriters. Writers like Bob Dylan, Paul Simon, Brian Wilson, Dave Brubeck, Joan Baez, Burt Bacharach/Hal David, Frank Zappa, Neil Young, Leonard Cohen, Lenny Kravitz, Madonna, Alanis Morisette, the list goes on and on and on. A lot of these people also reveal how many songs they write, wich seems to be different for everyone.