First, that's almost all the time for me because my primary use case for listening to music is in the car. Second, adapters are not a good solution because they can easily be lost.
I use a Bluetooth audio receiver in my car. It has a Jack output that you can plug into your car's amp. You connect your phone to it through Bluetooth, and then you can play music in your car. It's very convenient, because your phone automatically connects when you turn it on, and you don't have to mess with cables. They're also pretty cheap.
