25,000 miles is low, they should last much longer than that. Possible reasons: cheap crappy tires (name brands cost more for a reason-they're better!). Misaligned front end or bad shocks causing excessive wear. Under or overinflation. Unbalanced tires. Driving like a crazy person. Rotating them every 4 - 6000 miles will help even out wear.
Appropriate tires need to be changed after every 20000 to 25000 miles. However, if you find your tires to take more than this, then you are probably overworking them. This is dangerous and can cause tire burst while driving.
You need to rotate your tires every 3,000 to 4,000 miles to get the maximum life out of them. I buy tires that are rated to 40,000 miles and rotate them about 3,300 miles and I make them last till 55,000 to 60,000 miles.