It depends on what you call marketing!! Responding to enquiry emails is marketing,
SEO is marketing, keeping websites up to date is marketing. I don't spend much time comment posting, article writing etc, but I do spend time on twitter as I see results from that. Link building, gosh, maybe 1/2 day every month (an over-rated activity in my mind).
Overall - 6 hours daily, I run several sites, but most is spent on one site (caricatures)