Ianto knew what working for Torchwood was like. Owen and Tosh knew what was going on. So did Suzie. They all knew that hardly anyone in Torchwood lasts long. A short, exciting career and then you die.
Gwen knows, she knew before she joined up. Even Rhys has worked it out, and has chosen to come onside and work with the team.
See, here's the thing: I hope Jack explained to Stephen what was happening, and why. I hope that Stephen knew what he was getting into. I hope he knew what the likely outcome was before he took on the job.
I really hope Jack had Stephen's informed consent.