Its good to switch up your sanitizing routine to keep the bugs guessing (and to keep you thinking about the procedure).
If you're using Star San, switch to Iodophor for a few brews, or vice versa.
Make sure you're using enough sanitizer concentrate when you make batches of solution. Make sure its well-mixed, and check the pH before you use it. If you're using it over and over or making it with hard water, the life expectancy (i.e. acceptable pH) drops off quite a bit.
I also heard on the Basic Brewing podcast that Iodophor was only "good" for about 24 hours. That was a new fact to me!