As an indie author, it's a good idea if you write frequently so you can publish often and keep readers interested in your work. But it's not necessary. What's even more important than writing? Consistent marketing.
My Girl Likes to Market All the Time
I may be taking a somewhat controversial stance on this issue, of this I am aware. Some may say what's a writer without the writing? But that may be wrong. Writers do not have to be prolific in order to be successful. I know I bring her up all the time, but I must point again to Margaret Mitchell. She wrote only one book. But after "Gone With the Wind," where is there to go? Jane Austen wrote a mere 6 books.
If you write great books, you don't necessarily have to write a ton of books. But you will have to do a ton of marketing, even if you only write one book. The key to being an indie author isn't in the amount of marketing you do. It's that you do it consistently.
How often should you write to book bloggers to get reviews? At least once a week. How often should you Tweet? At least once a day. How often should you blog? At least once a month. How often should you write? When you're feeling the creative energy to write. Are you getting the point?
Keep marketing consistently. Keep doing the same things regularly, and frequently, even when you feel like you would rather pull out all your hair instead. Get creative to find new ways to market and new things to say, but keep doing it so you can engage new readers. I don't care how much you market, or how much money you spend on it (because you can do it for free). But do something every single day, or you aren't doing all that you can for your books.