I have these hundreds of balls that are just too worn-out to play matches with (they're not completely flat but they lost too much pressure). I see two benefits of using them for practicing serves: zero cost, and they will be better for my arm, since I've had issues with golfer elbow, and practicing serves too much (with improper technique while being too tense), contributed to that. On the other hand, I'm wondering if it would be a bad thing since these balls do not replicate exactly the sensation of new balls that I will be using for matches. What do you think? If I practice too much with these balls, will it hurt my serve more than helping it? Thanks.