Short-term viability may seem redundant to robustness, but it is not. This is a largely economic concern; not usually associated with ethics but I prefer ethics that are usable in the real world to useless abstract principles, so it should be considered. Companies need to know whether or not a business plan is viable before they open themselves up to the potential damages that Napster faced... before settling with the music companies, Napster was looking at hundreds of billions in claimed damages. But this is not the real reason that short-term viability is necessary.
It is common knowledge that the technology industry moves much faster then the legal system does. This is wrong. In reality, the legal system merely moves much less often, and deliberates those moves more carefully, then the technology industry which has a more continuous flow, with constant little changes.
The legal system may move rarely, but when it does move, the moves are massive! The Digital Millennium Copyright Act changed a whole lot of things when it was passed, and did it very quickly. Overnight, a large number of previously viable activities became illegal, and a much smaller number of previously questionable legal activities became well-determined. For instance, nobody knew how much legal protection was gained by putting access restrictions on something; the DMCA cleared that up, regrettably in favor of giving any restriction whatsoever full legal protection. Also, a large number of other activities that were previously not illegal in and of themselves, such as bypassing access restrictions, became illegal. The tendency of the legal system, especially the legislative branch, to produce huge changes is the basic reason it is necessary to deliberate so carefully in the first place.
If a solution makes sense in the short-term, this basically means that there aren't any technologies that can suddenly pop up that create contradictions in the solution. This means that while the legal system may take a great deal of time to arrive at a conclusion, if the solution makes sense to most people, the government should act predictably. Predictability is generally good in a government.
If ethical and applied-ethical (legal) solutions won't even work next month, then of course it's simply a waste of our time!