Do you market all the sites equally or just leave some to market themselves i.e. get natural links and wait for it to get picked up by search engines, repeat traffic, etc.
I don't own any sites myself. But some people i know who own many, tend to really just leave some of the sites to get on with it. However they do add them on search engines and so on.
It depends on the site Most of them I market all the time some that are not going to grow much I start up and then leave them to age
Depends on the site, usually I hardcore market a new site for couple of days and then leave it to do it's magic. Then I monitor if the siter are growing or not and give those who need it a helping hand with more marketing.
Every site should have at least some attention, or you might as well not have them. So they should have some content and some energy should go in building (free) links to that domain. But it is very reasonable to focus on one or a few at a time.