I have a couple of questions regarding the rackets we use. 1. Does constantly using a head heavy racket decrease ur swing speed in time? 2. Isn't it better to switch the rackets to a lighter head from time to time to maintain our swing speed? This is because i remember a video from Zhao & Xian doesn't recommend to train too long using the tennis as it may deteriorate their swing speed. i just wonder if this might also extend to badminton rackets. Thoughts?