The good news is that with Android 9.0 Pie, that is something users will no longer need to do. As confirmed by XDA, one of the new features of Android 9.0 Pie is its ability to memorize Bluetooth volume levels between devices. This means that volume levels will be adjusted automatically which means no nasty surprises when you pop on your headphones.
This isn’t actually a new feature per se as we had heard about it back in April. However according to XDA, the feature in Android 9.0 Pie was confirmed by XDA Inactive Recognized Developer Rashed97 who discovered it in his Essential Phone which recently received the update as well.
Android Pie was released yesterday but unless you own a Google Pixel handset or the Essential Phone, you will have to do a bit of waiting before you are able to get your hands on it. We expect OEMs to start detailing when the update will be released so do keep an eye out for it.