I have a six month old lab and am just wondering about the length of time I am walking him.  For about the last six weeks he has had about 20 mins in the morning and 15 mins at lunchtime.  These walks are on the lead.  At weekends we usually let him have some free running at the woods for 30 mins or so.   Is this too much?  I am aware of the problems of over excercise in large dogs so don't want to over do it.  Any advice would be appreciated.

As very round figures, 5 minutes per month of age per walk. Therefore at 6 months, 6*5=30minutes. So you are not far out.

The 5 minute rule is a nice and easy way of gradually scaling up the walking as a puppy gets older.

Best wishes, John