I've been in the same customer service position at a Supermarket for 5 years, but I'm now in store #4. Besides store #4 being an absolute mistake (everyone is insane), I've survived okay. Funny thing is Centrelink may move me to the dole next semester (study allowance only covers minimum course length plus one semester, this is my "plus one semester") so I will have to quit.
In terms of my survival I have an innocent face and I've employed my acting skills to take advantage of it. I spent the first year playing the customer service assistant role until I got used to being one. I've also concentrated on being good at tasks which take me away from customers to help give me a break. Also when I've gotten regular shifts I've developed routines around them to help me prepare for them, such as having coffee before I start, arriving a bit early and planning my breaks to include food and drinks with minimal rush.