I dont think you can measure marketing using time. There are a number of variables for instance what are your objectives in the short term as long as short term , your budget hence might spend less time but pay others to do some of the work.
I have many, many sites so I spend a lot of time marketing: article marketing, social media marketing and email marketing. I guess it depends on what type of site you have and the results you want to achieve. I own blogs, websites, text ad exchanges, credit based safelists, a traffic exchange and other VRE. Each site has to be marketed to different people in different ways.... Hope that info helps..
If you are referring to how many hours a day you should do your own SEO, then you should plan to devote 1 -2 hours each day, Monday through Friday doing SEO. If you don't have that kind of time, outsource it! Hope this helps.
and try to restrict the amount of time you spend browsing around and not really "doing" *guilty as charged!*
Spend a few hours a week marketing an e-commerce site. We have great organic traffic, but recently beginning to slide.
I spend about 1 hour per day checking up on my team, and answering a few emails. IF I am working on a new project, I'll spend a lot of my time working on that which can be around 5-10 hours per day.... that's only if its a product launch though.