A dog who is asyptomatic will do well as long as you're always mindful of the types of foods he eats and follow the proper protocol and avoid certain meds. Just because a dog is asymptomatic does not mean he can't become symptomatic later on. If wrong foods are given and certain guidelines are not followed, the liver problem can progress, cause damage and symptoms.
It sounds like your dog has more mild MVD, so that's a great thing as far as life expectancy goes!
I'm sure Logan will live a long and happy life.