Do marijuana plants die after some time or does the winter kill them, how long do they last?

They last until they are smoked.

I've had pot plants live 2+ years, but they do not live forever.

the cold will kill them and after you harvest there isn't much plant left unless your going to save one to put in a green house and use for clones.

All the cannabis varieties are annuals. You have to replant every year.

All plants eventually die as they become old and less productive.
ANY plant that is not winter hardy will die the minute the temps get below 32 degrees F. Some will last till colder and some go dormant but I think marijuana would die off in cold temps.

Cold weather kills them. They can last many years if they are keep warm enough.

its bad for your health dont do it please! kale is better for you <3