Songwriting is a lifestyle, if you try to deny it the words and tunes play in your head much louder than any other thoughts you may be having. Being the mother of two young boys I find my most productive songwriting time is after 9:00 pm. I do carry a blank page book and a pen with me every where i go . I just don't know when the music in my head is going to start playing. As far as too long if you spend more than 10 minutes on a single line for a song, you are working to hard. Think about something else for a while and the solution may present itself.