Upon hearing the classic line of 'I preferred the old one' when I changed a shuttle and took the following point, I wondered does it say in the rules that you have to change for a NEW shuttle? Its server's decision, so would my opponent have actually been allowed to get the old shuttle back when it is their decision?
Umpire's decision in international badminton, no set rule for plebs like us just like line calls, you'll have to come to an agreement. Although it's actually the only thing that I've never seen start a discussion, usually both parties agree (and who wouldnt, a new shuttle is always better!).