Our dogs demand twice daily walks--rain or shine, snow, dark of night....etc. The only times they don't get a walk is if it is icing outside or I am too sick to walk (thankfully both events are rare). At his peak Barkley was walking 4 miles a day. Now he gets a total of 2 miles since he is over 12 and he's getting slower if we keep him walking too far. Barkley has an alarm clock inside him and he lets us know when it is time for his walks. Toby, almost 6, is still extremely high energy so he gets 4 miles, and several retrieves (if it isn't too hot for him). We also do vertical retrieving which is tossing a ball from our upstairs "bridge" down to the family room. Toby will locate the ball while upstairs, then run down the stairs, retrieve it, and bring it back up to us in a matter of seconds. The humans are nice and tired every night--Toby, well, he brings his ball to bed just in case we want to toss it in the middle of the night.
Both dogs have a protected course to run from inside the house, through the garage and outside into the backyard through two sets of doggie doors. They use it regularly to go outside to chase squirrels, birds, respond to neighborhood dogs and do business. Running up and down the stairs to check on us also is good exercise for both of them.
I also believe good exercise includes mental stimulation. We try to stimulate their minds by letting them window and storm door watch daily. Both are very good watch dogs. Walking also stimulates their minds.