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.

If you figure that your confidence in any prediction decreases exponentially in the future because each second is an independent opportunity for weird things to happen, then the preference to cure cancer now falls out with no need for additional time-based preferences. You then need special confidence calculations when relativity is involved, but that's reasonable.