It depends what you want really. If I had to plug my phone in every time I got in the car, I can can guarantee that it would be disconnected 90% of the time. I always have my phone in my pocket. I bought a 64gb iPod touch which I keep permanently in my arm rest compartment and my entire music connection is on that so my music is always available from the moment I get in the car. I can still make and receive calls with my phone in my pocket. A dock therefore really wouldn't do anything for me...It would actually be an inconvenience.
And as far as I am aware, there is no dock available for the iPhone 5 anyway!