I cannot say how long. But talking about what happened, I had survived for one month without eating Nepali daal, bhaat, tarkari when I was in China. Believe me I was weeping then eating Chinese cuisines. Most interestingly, I'm a vegan and I managed to have lots of veg stuffs over there.
I must admit that I've been lucky that I'm eating Nepali food from the day I entered Amrika :)