Rivers Cuomo from Weezer has claimed to have a very prolific songwriting approach as well, apparently at least for periods of time doing a song per day.
Apparently during the first couple years of The Beatles' songwriting career John and Paul would knock out songs very fast, within hours - they actually 'scheduled' time to work together in a time-boxed fashion, so they could fit in songwriting time around their otherwise hectic schedule. Now they didn't produce that many throwaways, but in a period prior to this over several years they learned ~500 songs by ear. They learned these songs well enough live and used them as tools to figure out how to light up a crowd, and more or less had a foundational vocabulary from which they moved forward with.