What is your take on food expiration dates for canned/bottled foods?

Specifically, do the rules change depending on whether the can/bottle has been opened, do they bear any relation to what is stamped on the outside of the container either before or after (or both) the time at which the container is opened? Does it depend on the specific product? I’ll use tomato juice as an example, as this is a real situation I just encountered and had to make a decision on, you can use that example, or use another product.

OK, so I had two identical plastic jugs of tomato juice. One had never been opened, but it had an expiration date about 1 to 2 months ago. The other jug of tomato juice was open and half gone and had an expiration date 13 months in the future. It did not look or smell funny, there was no detectable mold or fungus of any kind on the juice, but it was pushed to the back of my fridge, and I believe it to have been in there for a good 4 to 6 months.

So, would you in this situation…

a) use the bottle which SAYS it doesn’t expire for 13 months, even though you know it’s been open for 4 to 6 months and throw away the unopened bottle.
b) use the unopened bottle which SAYS it expired 1 to 2 months ago, because you trust that as long as it’s not opened, it would stay good, and throw away the open bottle.
c) use both bottles, the open one first and then the unopened one.
d) use neither and get some fresh juice at the store.

I felt more comfortable using the unopened bottle. What would you have done, and how do you regard printed expiration dates? Can some things be used a week, a month, a year after their date while others, regardless of the date you throw out x days after you open it? What are your rules?