Author Jodi Picoult writes a novel in nine months. Jeffrey Eugenides wrote Middlesex in nine years. Will Allison estimates his novel, What You Have Left, took seven or eight years to write. And Audrey Niffenegger wrote The Time Traveler’s Wife in four and a half years.
There’s no set answer to this question because there are so many variables. Do you write swiftly or slowly? How much research will this novel require? How quickly will you hit on the right point of view, or voice, or overall structure? Do you have one false start or seventy?
And issues are bound to spring up as you write. Allison’s What You Have Left began as several short stories that he would work and rework. Further along in the process, he realized they could hang together as a novel. Eugenides’ Middlesex, a story about Callie, a hermaphrodite, and her family’s Greek-American experience, required research to keep the story medically accurate. And he struggled with Callie’s voice, which had to encompass not only her own story, but also the stories of her grandparents and parents.
A novel will take as long as it needs. Give it room and keep writing.