That system is essentially what we have now, but less subtle. A 2% inflation target means that the purchasing-power of held currency is halved in 36 years.
Yes, it's essentially the same as inflation. Although this scheme does open the possibility of having some lesser dollar that's statutorily inflated while perhaps the greater dollar retains its value. That might make it possible to throw a massive slug of stimulus into the economy without increasing the money supply.
I would think the "easier" way of doing this is Federal Reserve dollars, issued (in Fed issued deposit accounts) at the start of a calendar period with the explicit and clear understanding to accountholders that these funds evaporate at the end of the calendar period (EBT/food stamps come to mind; depending on the state, your EBT/food stamps funds expire after about a year if unused).
I'm unsure how you get around folks who will launder this money into assets to counter the inflationary mechanism, unless you're means testing in some capacity, or you just don't care about the cohort who does this (which is a reasonable approach imho).
Who would want to be left holding the bag with the expired "dollars" at the end of the period? I imagine they would trade at a substantial discount from the beginning, being dollars in name only.
I think you'd find most people would spend every penny before the funds expire. Anyone who doesn't is likely not too concerned about the funds expiring.
I don't think we can say for sure without a proper experiment (although if anyone can get their hands on EBT account spend data in aggregate, that would seem like a path to some signal, considering the financial condition of those who rely on those benefits).
