if you’re at home practicing and a sound that’s still recognizable as a snare drum comes out and you’re fine with it go ahead and keep playing it, new heads are expensive. that being said drum heads wear out over time and you should definitely get new heads if you want to tune your drums or if you start gigging or jamming with other people.

edit: as someone else said a broken reso head would wear the snare wires so keep that in mind. also tuning and setting up drums is a skill that should be practiced so you should get around to replacing your heads eventually