I have a 2013 C-max that I bought new. It crossed 300,000 miles just 6 days short of its 10th birthday (the day I bought it). I have not had any issues with the High Voltage Battery. Fearing the imminent collapse of the big battery is my main source of stress due to the miles on this car. I should also point out that My engine was replaced due to hitting a chunk of concrete in the road that did no body damage but went underneath and cracked the engine block at 180,000 miles. My insurance would only pay for a used engine with similar miles, but my dealer could only find an engine with 40,000 miles on it. So although my High Voltage Battery has 300,000+ miles, the engine Only has 160,000. I hope to get 400,000 miles out of this car, but I will be happy if it makes it to 350,000. I should also mention that I live in Michigan, but lived in Colorado for 4 years with this car. So, it has always been in a cold climate, and has been garaged I would estimate 97% of its life. I think the moderating conditions a garage provides has helped preserve Big Battery and also the fact that it gets driven every day.
