There are some best practices, [https://www.lifewire.com/tips-to-extend-iphone-battery-life-1999884|this guide] will help some, but as a general rule it is better to not charge your phone overnight or leave it while it is at 100%. Using it as a stereo will not hurt it, and it is always advisable to discharge it completely and let it charge to 100%. Also, if you do get a replacement, you discharge the new battery all the way before charging it. Hope that helped!