We judge an experience by its most intense moment and how it ends.
We don't evaluate a whole experience by averaging every moment in it. We judge it mainly by its strongest emotional moment and by how it ends, whether or not those moments are representative of the rest.
A hospital in Toronto split its patients into two groups before a colonoscopy. One went through the standard procedure; the other went through one that was three minutes longer but with lower pain intensity right at the end. Even though the second group spent more total time in the procedure, they kept a more favorable memory of the experience, and return rates for follow-up care rose by 10% among those patients. IKEA applies the same principle on purpose, placing its affordably priced restaurant at the end of the store's layout, to leave a positive last memory of the visit.
Memory doesn't store a whole experience with equal weight given to every moment. It mainly retains the emotional peak and the ending, and it's from those two points that we reconstruct the overall memory.
Source: Redelmeier, D., Katz, J. & Kahneman, D. (2003). Memories of Colonoscopy: A Randomized Trial. Pain, 104(1), 187-194.
In a long process that's necessarily uncomfortable (a bank procedure, a medical visit, a service complaint), what weighs most in the customer's memory is how the experience closes. A good ending can make up for an imperfect process.
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