If the distance from Nazareth to Bethlehem is 80 miles how long would it have taken Mary and Joseph to walk the distance?

Though it would normally take about 4 days to travel from Nazareth to Bethlehem, because Mary was nearing her pregnancy term and riding a donkey, it would require more than 4 days for fear of miscarriage. So perhaps a week (or more) would have been needed.

Various responses from our users:
The common form of travel in those days was by caravan, especially with long trips. Such a mode was far safer in case of accident or injury or possible attack by bandits, as well as being more enjoyable. With a census like this involving as many people as it did, a caravan going to Bethlehem would not be hard to find or join. Caravans would travel about 20 miles in a day, and the distance between Nazareth and Bethlehem (80 miles) would translate into a 4-day journey. on sale wedding options With Lace Appliques
It's worth noting, though, that the Bible never mentions a donkey - that's a later tradition.