"once effective" is a valid phrase to use in written English.
You can use it when emphasizing the importance of something being done only briefly or at one point in time and not continued after that. Example: Once effective, the new policy helped to reduce crime rates in the area.
There are ecclesiastical rules and precepts that were once effective, but now they have lost value or meaning.
The report, casting a wide net, said that many treatments once effective for illnesses, including viral ones, were being undermined through misuse.
We live inside the ironic spin room watching ourselves get shafted by our politicians, who use the same techniques once effective as a distancing device.
Once effective, many of these newer restoration tools will require the use of cryopreserved samples, especially if hybridization is desired between species with very different spawning times.
Indeed, the courts have largely abandoned once effective judicial decrees that forced integration of the schools and that might have overcome exclusionary zoning and other causes of residential segregation.
Another concern for Germany is the agreement that the new bailout fund, the European Stability Mechanism, can begin directly recapitalizing ailing banks once effective supervision by the central bank is in place.
Term limits could help ensure that once-effective sales leaders are replaced before situations such as the following arise.
Inappropriate use of antibiotics in both humans and livestock encourages bacteria to develop resistance to once-effective drugs, reviving the spread of diseases like meningitis.
The score so far: One imprisoned Russian business executive, the disintegration of a once-effective cartel that kept world potash prices high and political tension between the two countries.
As I went around Oslo's ministries, company headquarters and union offices (in a trip partly organized by the government but paid for by the International Herald Tribune), I witnessed none of the ideological squabbling that is now a hallmark of once-effective institutions, from France's labor movement to the U.S. Congress.
Most importantly, both courses of action have made clear that these once-effective systems are in dire need of regular adjustments to respond to the increasing complexities of today's pluralist societies.
