How long before you try a new food?

As many people already know I am having a hard time finding a food (dry) that Ping likes. He has been so finicky right now. I started him on Nutro Max Monday and as of right now he still doesn't really wanna eat it. And today is Friday so its been 5 days. How much longer should I wait to try something new and/or a new flavor?

are you mixing it with the old food still??? I usually give 5-10 days after the switch is complete to make sure they dont like it ..

A little yes...But he quit eating the old food thats why I had to find something different.

Does Ping react to a change in diet with diarrhea and/or vomiting? If not, you can basically try something new at any time. I know some owners don't agree, but I've been doing it for years now, and the cats in our local shelter also get different foods all the time, depending on what is donated or on sale, and very, very few have a problem with it.