Storage:
By definition, butternuts are a storage crop meaning that if you store them properly, you can keep them for months! They like a cool, dry place with good airflow and lack of sunlight. Check it regularly for signs of softness, mold or wrinkles; if you notice those developing early, you can easily save most of it by preparing the squash promptly and cutting out the soft parts. 

Use:
The way we prefer to prepare butternut squash:

• Preheat oven to 400 degrees.
• Rinse the squash under water to remove any dust or dirt.
• Cut off both the ends: the base and the stem.
• Cut the squash in half lengthwise and scoop out the seeds with a spoon; reserve for later.
• Using a vegetable peeler, peel the skin off in thin strips. 
• Chop up the squash flesh in 1" chunks.
• Add a healthy, saturated fat to a roasting pan or cookie sheet (try: lard, coconut oil, bacon grease, ghee, or butter)
• Arrange squash chunks in a single layer in the pan, and place in the oven for 20 mins or until soft.
• Meanwhile, rinse and remove pulp from seeds, and toss in olive oil, salt, pepper, or herbs.
• Place them in a single layer on a cookie sheet, and toss them in the oven as well. They're done as soon as they're golden brown! 

Both the roasted squash flesh and seeds can be used in a variety of dishes, or great just eaten as a snack!

Sources:
New Whole Foods Encyclopedia by Rebecca Wood
Produce: A Fruit and Vegetable Lover's Guide
And, our own experience!