How long would you be able to be a vegetarian for?

I need more information!

Are we talking of my own volition or against my will? What is the nutritional level of the vegetarian diet? What about tissue culture steaks? What about GMO based plant-cow-BBQ-steaks? What is the world food supply like? What about the local and regional supplies? What is the soil fertility level? Any ongoing mass insect extinctions going on? How are the bees? What about the weather? Is temperature the same as it has been more or less? What is the threat level of social anarchy?

I cannot tell you my answer without all of this information plus whatever I forgot to mention.

Otherwise I would say... indefinitely? and refer to my previous questions and statement.