Am 09.05.2017 um 22:14 schrieb Jonathan Masur:
.. Simon, I do not understand what you do mean when you think old boundaries "will eventually decay as they won't be maintained". There is no maintaining to do, since the border just is there and never moves ? Unless you're talking about VERY long term (thausands of years) when earthquakes and such will radically alter the landscape, but at this point I don't think computers will still be around, let alone OSM ! And of course old boundaries can be verified by looking at old maps which are past their copyright date. In many cases boundary stones are there too, although no guarantee.
The borders (current ones and others) get damaged, are partially deleted etc etc all the time. They increase feature density and make mapping more difficult, particularly because they tend to be near other linear features, keeping more boundaries around clearly doesn't come at zero cost.
As to the historic aspect: sure it would be interesting to have access to a full set of historic boundaries (AFAIK you can't even get that from BfS currently), but that belongs in OpenHistoricalMap or whatever it is called, not in OSM proper. Note on the side: I suspect we are talking about 1000s of additional boundaries even if we are just considering modern Switzerland). And in any case the "historic" tags are for historic objects that can still be surveyed not for objects that have gone without a trace.
Simon