In an interview Saturday, Anderson said one day is enough time to rest between spacewalks. He said he often played baseball doubleheaders and basketball games on back-to-back days.
"We're in pretty good shape for old men," he said, "and I think we'll be ready to rock 'n' roll."
Anderson is 51, and Mastracchio is 50.
Both are members of space shuttle Discovery's visiting crew. They have another week at the space station before departing.
Discovery arrived Wednesday with tons of spare parts and science experiments for the space station. Much of that was in a cargo carrier that was attached temporarily to the station. One of the big-ticket items being transported Saturday was a darkroom-type enclosure for the U.S. lab's high-quality window, designed to improve picture-taking.
The 13 space travelers' workday was interrupted early Saturday when a smoke alarm went off in the Russian living quarters. It turned out to be a false alarm, set off by dust apparently kicked up by filter cleaning. The astronauts scrambled for about three minutes to make sure there was no fire before going back to what they were doing.
Like many at NASA, the astronauts in orbit are anxiously awaiting President Barack Obama's upcoming space policy speech. Obama will visit Kennedy Space Center on Thursday and discuss the future of NASA's human spaceflight program.
In February, Obama canceled NASA's effort to return astronauts to the moon and placed added emphasis on the development of new technologies. He also extended the working life of the space station to 2020.
Only three shuttle missions remain after this one. When the fleet is retired this fall, the space station essentially will be complete. Thousands of jobs will be lost when that happens, many of them at Florida's shuttle launch and landing site.
"Life is full of changes, and change is hard," Anderson said. "We'll just have to see how it all falls out."
Added Mastracchio: "No matter which direction we take, I think NASA's going to be a big contributor to technologies and new ideas and manned spaceflight."