Walz, making his fifth space flight, also took another endurance record away from Lucid Wednesday, becoming NASA's most experienced astronaut with more than 223 days in space over five flights. The world record belongs to cosmonaut Sergei Avdeyev, who chalked up 748 days in space over three flights.
Bursch and Walz were asleep at the time they set the record. Shortly before bedtime, though, Mission Control reminded them that they soon would be breaking Lucid's mark.
"Of course, you all have a long ways to go if you're going to break the all-time single flight record of about 438 days," Mission Control said. "Do we have any volunteers today to go for that record or will you guys be satisfied with the one you have?"
Bursch, Walz and their Russian commander, Yuri Onufrienko nodded their heads. "I'm very happy," Bursch said.
Flight director Rick LaBrode said Bursch, Walz and Onufrienko have been "nothing but positive and really go-getters" from the time they rocketed into orbit on Dec. 5.
"I don't know if they're happy because they're coming home or they're just being their normal selves, but they're doing just a great job," LaBrode said.
If Endeavour had launched May 30 as planned, Walz and Bursch would have missed the record by about six hours, but rain delays and hardware problems kept the orbiter on the ground an extra week.
"For me it's quite an honor just to be mentioned in the same paragraph as a great American like Dr. Shannon Lucid," said Bursch.
Two of their shuttle colleagues, meanwhile, wired up and bolted down a work platform Tuesday that will allow the space station's 58-foot robot arm to roam across the orbiting outpost.
Franklin Chang-Diaz and Philippe Perrin connected eight power, data and video cables. Then, working 240 miles above Earth, they drove four bolts to secure the platform and installed a TV camera.
On Thursday, the same pair is scheduled for a third spacewalk to repair the wrist joint.
The two spacewalkers account for much of the international interest in this flight. Perrin is a French astronaut and Chang-Diaz is a U.S. astronaut born and raised in Costa Rica.
Earlier this spring, 44 feet of track and a rail car were installed on the international space station for use in the later stages of construction. Tuesday's work involved bolting a $254 million platform on the rail car.
The platform will enable the robot arm and pieces of the space station to ride from one end of the complex to the other. A series of tests must be conducted over the next few weeks before the robot arm is commanded to climb onto the platform for a ride.
Eventually, the rail car will run the entire 356-foot length of a framework that is being installed at the space station.
The 1½-ton aluminum platform was delivered by the shuttle last week.
Tuesday's spacewalk was the second one this week. Chang-Diaz and Perrin will go out one last time on Thursday to tackle their most challenging job: robot-arm wrist surgery. One of the wrist joints in the robot arm seized up in March and is being replaced.
CBS News Space Consultant William Harwood has covered America's space program full time for more than 15 years, focusing on space shuttle operations, planetary exploration and astronomy. Based at the Kennedy Space Center in Florida, Harwood provides up-to-the-minute space reports for CBS News and regularly contributes to Spaceflight Now and The Washington Post.