…seems to be 15-20 years. First, there was the Bretton Woods system based on the US Dollar from the end of the 1940s to 1973. It collapsed when the US Dollar couldn’t keep up with gold, to which it was pegged. Then, after a short period of floating exchange rates, came the ‘Exchange Rate Mechanism’ in 1979. It collapsed in 1992, when Britain and Italy weren’t able to keep up with the Deutsche Mark. Then came the Maastricht Treaty in 1992, laying the foundations of the Euro, which was introduced in 1999.
The Greek debt crisis of 2010 is comparable to the moment, when the Bretton Woods system came under real pressure for the first time. That was in 1968. Then it took five more years to finally wreck the system. Will there still be a Euro in 2015?
On an interesting side note: Continental Western Europe had floating exchange rates in peacetime for only 6 years in modern history, from 1973 to 1979. The US Dollar, the Swiss Franc and the Japanese Yen are floating since 1973. Did it work better? Yes and no. On the positive side, they weren’t drawn into debt/balance of payment crises. On the negative side, a floating currency can’t prevent the government from undertaking irresponsible fiscal policies.