I can buy a large can of tune here that will keep me fed for about 3 weeks, based on my usual diet. If I buy the large can, the cost is 60% of what 3 weeks of small cans would be but I am not sure if the tuna will last 3 weeks in the fridge. It is packed in "spring" water. Can tuna be frozen? Also, I have a seal a meal thing - can I open a can and then seal it into day size pouches?