John Scalzi is talking about why debut novelists are so often so much older than debut musicians or actors. I commented over there with my own timeline and it seemed worth noting it here too. Please feel free to post your own both here and there.
My novel publishing timeline:
1967 – 1991: Time spent learning to write well enough to write a novel (ages 0—26).
1991: Wrote first complete novel (age 26)
1992–1993: Wrote two more novels, one of which is possibly publishable with rewrite (28)
1993-1998: Wrote a bunch of short stories while trying to sell all three initial novels (31)
1999: Started selling shorts and returned to novels, writing the book that would ultimately sell first (32)
2000: Got agent who started marketing novel (33)
2000-2005: Wrote three more novels, all still looking for publishers (38)
2005: Contract signed for that debut novel (38)
2006: Debut novel published (39)