Port..how long does it last?

[uh1p]

I have never bought a bottle of port. However I have been mooching off of my friends for years. Now I'm ready to make the big plunge. My question is how long does it last after the cork is removed? I know regular wines deteriorate rapidly, but with the higher alchohol content of the port would that extend the shelf life? I just can't drink an entire bottle at one sitting, and would like it to last me for quite awhile. Is this even possible. Many thanks in advance, and my friends thank you too!