I've been writing for most of my life (I wrote my first story when I was six - complete with illustrations!) and I've churned out dozens of poems, short stories, and a couple of early novels. But it's been less than two years since I decided to make a serious attempt at an author career. In that time, I've written four novels (including a trilogy) and two short stories. Whether or not they're any good is not for me to decide, though I feel they are solid stories and I'm proud of these first steps.
I'm also proud of my writing pace. I rarely write for more than two hours a day (most days it's just one) and my average pace is 500 - 1,500 words a day. I try to write every two out of three days, though, and every day if I'm in the clutches of inspiration. At this rate, I can hammer out an 80,000 word draft in 3 - 4 months. Add another two weeks to one month for editing and then it's out the door.
There are many advantages to writing quickly as opposed to a leisurely pace. One, I get more books out there in less time, generating more exposure, building my back catalogue, and taking up more shelf space, thus giving the impression that I'm a serious writer who is committed to the craft for the long haul. Two, it keeps things fresh for me, so that I'm not sloughing through the same story year after year. Some people become very close to their characters and love watching them grow and develop, as do I, but it can morph into helicopter parent syndrome. Sooner or later, you have to send the kids out of the house, and sooner is usually better than later. This brings me to my last point, and some may not consider this an advantage, but I do. My quick production rate keeps me from becoming too attached to the project, so that if it doesn't sell well or it gets cut down by readers and critics, I won't be utterly crushed watching my life's work get stomped and spit on. I hope this doesn't happen regardless, but this way I won't get too clingy and become consumed by perfectionism. There are many great books out there that have gone through twenty drafts and are still languishing on computers because the writer is afraid to release it out into the wild. If my book sinks, I won't be devastated, because the next (and hopefully better) book is just around the corner.
Now I know that every writer is different, and I'm not giving advice to anyone. This is just what works for me. My fast writing pace suits the kind of books that I write, whereas someone composing an epic fantasy monolith probably shouldn't crank it out too quickly. I don't have any illusions about my books being high literature or anything; I just want people to enjoy them and be entertained.
Perhaps after I've established more of a name for myself, I'll take things slower and go deeper. I don't want to sacrifice quality for quantity, and as I said, I'm proud of what I've written thus far. I know I've still got a long, long way to go, but I'm not going to rest until I get there.