Obedience for a mature/finished dog can be boring, they are going thru the motions but not really 'learning' anything. I'd give him a break and do some other stuff to keep him engaged with you.
When we go thru this, I will use the line as a check and when the dog 'checks out', I turn the opposite way real quick and lose him. He then gets a self-correction for being away and it brings him back to me with some enthusiasm. He gets rewarded as soon as his focus is back on me in heel position.
I'd also change up my training style for awhile, reward randomly while asking for more(circles/turns/ups) when the dog starts losing interest, circle him, or ask for an up. When I say circle him, don't heel in a circle, but have him spin clockwise back into heel position, turns are the counter clockwise spin. Dogs learn these key words with some repetitions and it brings back the drive level when you use the key words.
Last edited by onyx'girl; 12-15-2013 at 08:44 PM.
Reason: sp fix!