Storing Porto after it's opened

[Puccino]

With the help of this board and other sources, my comfort level and knowledge of wine has increased nicely, but I must confess that until last night I had never tried Port (I guess it is called Porto?). I remember feeling this naive once upon a time with wine, so please forgive my lack of knowledge with this.

I researched some past threads here re: Port and found some discussion in 2001 about how long Port(o) remains drinkable after opening. Maybe a week or two weeks? It also mentioned tawny Port? What is that? All I know is that my wife picked me up a bottle of 1985 Porto (from Portugal), and that's all I know off the top of my head. We opened it last night (honestly didn't even know how to open the thing - how crazy is that?? Had the cork screw ready just in case!) and it was excellent!!
What do I do with it now? You mean I have to drink it all very soon?? Ah, nuts! I can imagine worse things!

Thanks for any input,
Puccino
(By the way, winoweenie, I've noticed a few mentions of OK from time to time - makes me a tad misty-eyed as my wife and I are both from there!)