In most cases, yes. It depends on how many metal parts your set has. Since the important parts – net and poles – are often made of PVC or nylon, it can be safe to leave your net set up for long periods. However, you will want to store the rackets indoors to protect the grips. If your net has metal poles, you don’t want to leave it outside, especially in the rain. The packaging on some sets may state that they are designed to be weather resistant.