yeah, you're probably right. i won't say it's impossible to own 5k different domains, but its a huge investment in the first place, and then of course a lot of work with all of them.
I have more than a few certainly but be careful, one website getting a low click through percentage will effect your overall profits. In that situation you need to take the ads off of that particular website.
That's why you are so busy with them that you don't have time to post here more often? I will believe what you told but when ... hell freezes over!