Well the reason you dont train your back 3-5x a week is because you rarely use your back. We have been using our calf muscles for as long as we have lived, so i think you should hit them hard. Maybe not 5x a week, but most people dont train them hard enough.
2x a week is good but make sure you train them hard enough to make them sore the next day ALWAYS. HOld the top position for 1 minute, do 100 reps, do 15 heavy reps in5 minutes, etc
theres so many differant interpretations man, some say the calf is meant for endurance so treat it that way and do alot of volume, others say it is used to the volume so shock it by using low volume. Some say treat it as any other muscle some say train them nearly every day as they are made and adpated to recover fast. I dont know man I think the main thing is hitting them with intensity and if they arnt responding to a certain theory of training then change, one things for sure if you dont change in input then you wont change the output, if you know what i mean