Kodachrome has a long life after being developed, but it can still be damaged by high temperatures before exposure. I would store it in the fridge and take it out an hour before you want to shoot with it.
Modern films reflect the current trend toward hyper-saturated color, but Kodachrome does not. The colors will likely appear somewhat 'flatter' than those of your other film if you compare them side by side. In my experience, the color Kodachrome gives are rich, but not saturated to the point of being unrealistic. With 64, you should see no real grain but still have nice, sharp images. With 200, the grain is a bit more apparent, but the colors are still natural looking.
- Randy