Here's my take. I take it to a Duc dealer for resale purposes. If I ever sell, I'll probably make up a fair percentage of what I paid for having a bike with all the records. I personally would never buy a Duc that was maintained by a shadetree mechanic, you have no idea how mechanically in/de clined they are.
It's not accurate to idly toss out blanket derogatory terms like "shadetree mechanic" to describe those who do their own work. From what I've seen most if not all the Duc riders who do their own work and independent shop owners are very conscientious, even to a fault. Not so for many dealers who have a reputation for overcharging and doing things like overtensioning cam belts and generally not knowing much. I personally would be more comfortable buying an owner maintained bike than a dealer maintained bike, unless the dealer was one of the few with an exceptionally a good rep.
And of course there are a lot of variables but I'm not sure how much of the high cost of dealer maintenance is recoverable at sale time.