It's tough to really tell if a yeast infection is completely gone or if it's just in remission. The best thing to do is to just stick with the diet and supplements for at least 6 months with NO symptoms. Do not just think 6 months with no symptoms, but stick to a good diet for 6 months with no symptoms. The reason I say that is because when you are on the diet, you are starving the candida, as well as fixing your body. If you go off the diet, you may get rid of the symptoms, but may get symptoms back in 2 years or so. The candida doesn't grow overnight, and doesn't heal overnight as well.
Look at this answer by Sean for what he recommends http://candidaquestions.probacto.com/440/believe-cleared-myself-from-candida-long-should-stay-this-diet