How many miles can I expect to get on my brakes for a 2004 Highlander?

It greatly depends on several factors such as driving habits, climate conditions, and the topography where the vehicle is operated. Generally, you might expect to get anywhere between 40,000 to 70,000 miles on your brake pads. But it's a good practice to have them inspected regularly (such as every 10K to 15K miles) for signs of wear and tear, and replace them when necessary.