I think we can all agree that the world would be better off if we delayed implanting the discomforting device by 10 minutes (or equivalently implanted the pleasurable device 10 minutes earlier). If you dispute this conclusion then you get absurd results if you even admit the possibility of a universe that exists forever as in such a universe it is no better to permanently increase human welfare now than to delay that increase by 10 minutes or 10 centuries.

No to both. Delaying eutopia seems bad because we'll experience something bad in the meantime. Pausing all of reality for 10 centuries is not even meaningful, and pausing only humanity seems neutral if (implausibly) it does not affect the total subjective duration nor the quality.