I like them, but would probably never own one unless I'll ever own and regulary use a dog sled.

Oppositional Defiant Disorder is just native behavior to some breeds...

One example that comes to mind is planting new grass seed on the lawn, and she was not allowed in the grass. She pretty much instantly figured out the new rule, but would constantly test it. Drop her ball a foot into the grass, then lay down on the sidewalk and crawl into the grass keeping her hind legs on the pavement. Still on the sidewalk!

It's a constant battle of wits trying to keep her from figuring out new "loopholes" or grey areas we don't anticipate. Also finding her "jobs" to do so she doesn't make stuff up on her own.

When I research a topic, whether it's an engineering diagram or looking up a half-remembered recipe on my phone, I immediately engage. It's fulfilling, not tedious. It can lead to "being in the zone".

It doesn't mean it's not taxing, but there's definitely a positive feedback from my system. Probably the same feeling if you're watching the water for a fish to spear, or watching your dad to see how he spears fish, or watching your mom to see how her lips move when she says "Mom". Or the ball to see when it's thrown and where, or if cars are coming because then you need to stay still and keep your human from proceeding.

Apart from the clients workplace, the service dog will be on and off duty for the rest of the day depending on the specific needs of its client. It follows them wherever they go (supermarkets, doctors, museums, whatever).

The dog can play or relax during breaks, or in the evening, when the client is in a safer/less stressful environment.