Well, not quite 10, but I have 3 selling sites, 3 blogs, a small forum, and a new Squidoo lens, so eight thus far.

I give priority to my selling sites, and try to keep the rest up in the air like the proverbial spinning plates. That includes adding new content, and the promoting of them.

Some are more important than others. You can never have all sites equal as value.

I have 4 high priority sites, 3 low priority, and 25+ that I forget about, and work on now
and again.

Marketing is spent on the 4 high, with the 3 low worked in "organically" when I can. The
others are all organic.

Yes, I think that out of the 120 plus we own - I'd say about 8 are the ones we really concentrate highly on.

This is not to say we neglect the others. The others are there for a reason but not for the same as our main sites!

Usually concentrating on the newest and most profitable ones. The rest I try prioritize in the order of better potential for profitability...