We should perhaps let Impaler respond, but I feel compelled to comment on this;
you must be punished with a currency that loses value over time, so that you can be encouraged to be as wasteful as everyone else.
I guess that could be put more nicely. The bottom line there likely is not to promote wastefulness, but progress, growth, evolution and all the good stuff.
The idea of accelerating progress through enhancing flow of value is starting to reveal upon me.
Saving is stagnation. In nature, saving achieves little as compared to swift exchange of value. Keeping things stationary - whether material or immaterial - is subject to heavy corrosion. In all things, time eventually eats your value through entropy if you don't use it.
As long as a human monetary system obeys the laws of nature, the same would apply there. It's not difficult to imagine how keeping money off circulation (saving) does discourage initiative and achievement => increasing entropy (= what we generally consider the opposite of "good").
I'm not versed enough yet on demurrage to conclude whether that would be the holy grail. The issue of wastefulness as a side effect of quicker value flow is the flip side, but how serious.