me personally I always check the bigger bearing and always replace the smaller one, nova's are probably better quality so thats up to you, check them at the very least is what I would recommend. And for our A-B mains are 30 mins so ill change them anyway but C and below seems to be 20 or 15min so I wouldn't change them. But if you buy name brand chances are they're better quality and don't need replacing like I do, Just something I do

Hope this helps