This is a question for the more experienced affiliate marketers here on the forum.
Let's say......you currently have no profitable campaigns and are down to your last $5,000 or something.
How many campaigns do you launch and test each week?
How many hours a day are you putting to pick yourself up again??
There is not set rule about this mate.
If I were in that position I would spy as much as possible and then put all the time I had into launching / optimising.
I would try to understand why you are not profitable first, before trying to find a solution.
$5,000 is a LOT of money to be working with
I'd start first with research. Talking to friends, affiliate managers, researching STM, and spying on the competition. What I'm looking for is a nice match between a traffic source and an offer.
Example if this was a few years ago then Credit Reports + PPV could be a choice. I could conclude that other people are making it work, so perhaps I can too.
After that it's just a matter of launching and testing. There's no set answer as far as how many to launch. Rather I'm launching and making sure I'm spending enough to gather data.