[j3ffr0]

All the examples cited by the OP are songwriters who are first known as performers. I'd say that most of these artist/songwriter types do have a shelf life. Some combination of the public moving on (things going out of styes), as well as them having a limit range of that performance thing they do as well as that song writing thing they do.... however brilliant... range/style/genre limited.

I would say that professional song writers who's names are much less common in the public do not have as limited of a shelf life. Some have specialties.... but they don't have a following that expects to hear certain things from them. They have chosen a profession where they are not in the public eye as much as an artist/songwriter. I can't really think of many, because their names are known to me either... but perhaps Ala Menken is an example of someone who eventually achieved success as a song writer. He was good enough to get paid to do work, and he did good enough work that he continued to get paid to do more.

Also worth noting that there are many great songs that no one has ever heard by songwriters and artists that no one has ever really heard of. Songs sit there unconsumed.... some age better than others, but the truly great ones don't expire... even if no one really hears them.