I have a large yucca, and they seem to be very thirsty. It's about 4 foot tall and is in a 5 gallon pot, and I often pour in a whole pint of water which it seems to asorb entirely. Aparently you should water a lot occasionally, not a little bit every day because they do like to dry out in between watering. You'll get used to your plants over time, I know mine needs one pint of water twice a week and feeding once a month, but the size of your's means it won't be the same.

Oh, and if you can it would prefer to be in a bathroom or kitchen for higher humidity, perhaps even a humidity tray under it would help? You can easily make your own with gravel on a plate.