Don't wait to replace your Lexus ball joints if you know it's time to.  Ball joints are crucial parts of your suspension system.  They are the pivoting points between your ties and suspension.  Your ball joints are also there to help support the weight of your vehicle.  Some vehicles use their ball joints to formulate their wheel alignment settings.  Every car and truck on the road requires their own ball joints.  Older model vehicles and vehicles with high mileage usually end up needing to replace parts of their suspension systems at some point.  If your ball joints are damaged, you will have a hard time trying to pretend like you don't notice.  You'll feel a shaky sensation while you drive and it will be impossible to get your vehicle driving in a straight, smooth line when you're having suspension problems.  In many cases, loud, clanking noises will come from your vehicle as you drive over bumps with poor suspension.