Inspect the tube. If good, reuse. The biggest failure point (non-puncture) is around the valve stem. If where the valve stem meets the tube is in good shape and no other tramatic events to the tube, keep using. If the tube is starting to crack and split anywhere, most common at the point the valve stem joins the tube, time to toss it and get a new one.
I generally go 2-3 tires before I get a new tube. Providing the tire didn't spin on the rim shreading the tube.