If you’ve been around Internet marketing for more than 5 minutes, I’m sure you’ve heard about the importance of split testing your landing pages. I believe that the only time you should stop split testing, is when your conversion rate reaches 100% (which honestly won’t ever happen).
I’ve had an old campaign running with search traffic that I haven’t touched in about 2 years. It doesn’t get a ton of traffic, but makes a consistent profit of $50-$100 a day. I got lazy with the campaign as I have just had it on autopilot.