The Supreme Court announced Monday that it would hear arguments over three days in late March to decide the constitutionality of President Obama's healthcare law, another sign the justices see the case as a once-in-a-generation test of the federal government's regulatory power. The 5 1/2 hours of argument are believed to be the most time devoted to a single case since the 1960s. In the 19th century, the justices often sat silently and listened to arguments over several days in one case. But in recent decades, one hour per case has been the norm, even when a major constitutional question is at issue. The lawyers for each side normally have just 30 minutes to state their cases and answer rapid-fire questions from the bench.