I've read back old posts and very few of them actually state three times a day so I reckon there may be a few people that have made the same mistake 
I agree Jan - it is only fairly recently that the five minutes per day rule seems to have evolved into a five minutes per walk rule 
Like I said, probably it depends on the puppy. Alfie would have done himself more damage running riot in the house if he hadn't had a bit more exercise as a puppy than an extra 15 minute stroll on the lead could possibly do him. The KC recommends 5 minutes per month twice a day as far as I remember but I did three because I felt that that was right for my dog and I have read others recommend this also.
Apologies to the OP as this thread has gone waaaaaaay off topic!