My sites that do best are the ones on either generic domains that get the type in traffic, and you just need to have related ads/products on there to make money. Or, the sites that I spend the most time and effort on for original content (blogs), also get the traffic.
I think you only need to have one idea or site to do well, just make sure it would have a decent size audience and if you do it well and have regular content, it should make money. If you spread your efforts out over too many projects then none of them get done well, unless you have a team working under you.
you are perfectly right.,of recently i ve decided to focus my attention on just 3 domains.
cheers
Or, spend up for a category killer domain (eg: Bobbleheads.com) and sell the product for the category.
Problem with most domainers, myself included, is we have too many ideas and domains to do them all well. Some of us would probably be further ahead if we focused heavily on just ONE or two things, and did them well. It also really helps to have an interest in the subject you pick, because then it wont seem so much like work.