I hate to confess this, but a big bottle of nuoc mom or nam pla will live forever in my fridge, and much as I love Asian food, this is a pain. I cheat and use anchovie paste or even for some dishes Worcestershire sauce (which has fish sauce in it!). NO, it isn't THE SAME, and the dish will not taste as perfect as the one at the restaurant (which is why I go to restaurants). But in a pinch ..... I cheat. The paste takes less space in the fridge and works in a pinch. Obviously if you're a vegan, none of the above works.