关于“你们每天用手机多久”的英语表达，可以有以下几种方式：
1. How long do you spend on your mobile phone every day？
2. How much time do you spend on your phone daily？
3. What is the duration of your daily mobile phone usage？
结合以上表达，你可以根据自己的需求选择合适的问句。例如：
"How long do you spend on your mobile phone every day？"
"How much time do you use your phone daily？"
希望这些表达对你有所帮助。