How much sleep does a 13 month old golden need

Question
Hi. Life with my 13 month old golden is getting a little easier every day. He is starting to understand who is the pack leader:) We want to know on average how often does a golden his age sleep a day. Is there an average amount of sleep and exercise best for him. He would exercise forever if I had the time, could you lead me to a better balance. I work from home a lot and I can't dedicate every minute of my day to him as he probably would like. How do I make sure that he is getting enough sleep and exercise? Just in case this can help you in answering me. He is approximately 90 pounds, he is not fat or too thin, he has a nice coat and he is very playful.
Thank you for your time  

Answer
Try to get in at least a half hour of vigorous exercise each day.  Fetch or other running games are good.  All the walks you have time for.  From there, let him sleep as much as he wants.  Dogs have a great facility for sleeping when nothing else is going on.  As long as he get plenty of exercise, it doesn't hurt how much of the rest of the time he sleeps.