Nothing lasts forever, especially something we use frequently. Your brush sees action either before or after every grill cooking session (and if it doesn’t, it should!), meaning it’s highly prone to wear.
Take a good look at your grill brush. If the head or the handle are cracked, it’s time for a new one. The cost is so low for a new one, it’s not worth the risk of injury from a broken, jagged edge or bits of plastic getting into the grill’s cook box.
Mangled and bent bristles or wire coils on bristle-free brushes are also clear signs that your grill brush has had its day. Damage like this will keep it from cleaning effectively and could be detrimental to your gas grill’s grates.
Most importantly, if you use a grill brush with metal bristles, look for loose bristles before every use. You can use a pair of pliers to tug a few bristles gently as a test. If a bristle detaches and sticks to the grate, it can end up in your food and then in someone’s digestive system. This is extremely dangerous. At the first sign of a loose bristle, trash the whole brush immediately!
Keep an eye out for rust, by the way. Rust is a good sign that the metal in your brush is losing its integrity and is liable to break. If the brush is seriously caked with food debris but otherwise intact, a good cleaning may be all that’s required to restore it to prime condition.