Interesting concept, but it will never happen with the amount of pull (and money) drug companies have:
Limited-time drug licensure would furnish incentives to ensure that all new drugs are properly scrutinized. Companies would need to formulate post-marketing surveillance plans as well as promotional plans when a drug is approved. The FDA would be subject to firm deadlines in reviewing post-marketing information, because prescribers and patients would be relying upon a seamless system of licensure renewal in the absence of negative information.
