You get what you measure. That's one of the fundamental truths of Quality Assessment. If people know they are being held accountable to a standard, they generally perform to that standard. By the same token, if they know they are not being measured, their behavior will often ease back into old habits (I've been able to quantify this effect with data). It's important for a quality program to keep momentum.
I was recently reminded how critical it is for smaller contact centers to be prepared for turnover in their quality team. It is quite common for call centers with less than fifty seats to have one person who handles the quality process. If tragedy strikes or that person suddenly leaves, the contact center can suffer an agonizing lapse in their process. As a new person gets up-to-speed, the floor eases back into old habits and, after taking three steps forward, you find yourselves two steps behind.
Wise King Solomon reminded us, centuries ago, that "two are better than one." If you are operating a quality program in a small contact center with one QA analyst, you might give thought to initiating redundancy. Make sure you have bench strength to carry you through, if and when you should need it. Have a person trained and warming up in the bull pen should you find your QA ace suddenly in need of relief.