How do you split your time between development and marketing?

In his recent year-in-review newsletter Max Rozen, of OnlineOrNot, wrote about how he spent too much time worrying about feature gaps and not enough time marketing, which really resonated with me. I probably spent around 10% of my time on marketing last year, with the result you'd expect.

This year I want to spend more time on marketing for SavvyIdeas and am thinking of doing two weeks of dev followed by two weeks of marketing (which could include documenting new features from dev weeks and adding them to the marketing pages).

Will this work? I'm not sure. To be honest, I wonder if spending 50% of my time on marketing will be enough, though given how much I don't enjoy it, it feels like too much.