They deteriorate based on time, not mileage. Although not changing your brake fluid at proper intervals can negatively impact the life of the hoses.
If you plan on keeping the car for another few years, I would just go ahead and replace them. If you plan on getting rid of it in the next 2 years I would inspect them. Look for cracks, bulging, twisting, etc. And then feel them to see if they are soft and squishy, or hard and brittle.
I have heard that brake hoses only last 6 years on average, but that is not true in my experience (it may be true in places with harsher weather than Florida). I would say that around 10 years would be a good point to replace them for someone who plans on keeping the car. They are definitely one of those items that "better safe than sorry" is a valid reason for replacing.