i write alot of story type songs for country, i use them to wrap up the lyrical tension and tie up any loose ends between the characters. I also make this the absolute crescendo of melody for the entire song and then i usually run back to the chorus and then run for the exit...musically the section is different from the verse and chorus, maybe a minor thrown in to differentiate it,or a key change, i do some modulations there and come back to the chorus a step up to keep the build going...2 lines, 4 lines are common, 6 lines it better be a tempo as bridge sections for commercial writing are something to kind of get in and get out of timely. All that said, i don't always use them...the song will dictate what it needs , and if you have any questions on a particular song, most here will be glad to offer our opinion, so long as you offer us yours...ha...write great, be well...moker