It's enough to give some veteran astronauts food for thought on what the future holds for them beyond the shuttle, while others remain committed to the long-duration missions that will be the only available rides until NASA renews manned lunar treks by 2020.
"One of the things that you're seeing now is exactly what happened with Apollo," said Roger Launius, a former NASA historian who chairs the Division of Space History at the Smithsonian Institution's National Air and Space Museum in Washington, DC.
"As people began to see that program wind down literally, astronauts were beginning to leave the corps," he explained.
NASA's Astronaut Office is doggedly working to preserve its base of experienced spaceflyers and planning to swell its ranks with a new group of up to 15 astronauts in summer 2009.
"We'll certainly have people retire as they get older, and they decide to go off and do another career. We'll see a lot of that happening," said four-time shuttle flyer Steve Lindsey, chief of NASA's Astronaut Office.
"What I don't want to see is us hit 2010 and all of our experience walk out the door," he added.
There are about 90 astronauts on NASA's flight roster today, with less than six still waiting for that first assignment to a space-bound crew, said Lindsey.
Somewhere between 10 and 15 new astronauts may join up in the new class, though the actual number remains to be seen, he added.
"One of my objectives is to get everyone in the office flown by 2010," Lindsey said. "And my current projection is we're going to be easily able to do that," he added.
According to Lindsay, the goal is to ensure NASA's astronaut corps is as experienced as possible before the shuttle fleet retires and ready to withstand the departure of retiring spaceflyers, yet still retain enough veterans to lead the incoming 2009 class of astronaut candidates.