The ones that I thought had no conscience were the ones that burned all their sick leave and then truly got sick and asked for donations of sick leave so they could survive. I call that God Smack.
Saw that all too often during my career, I did donate to a couple of folks that I knew did not abuse their sick leave, they just had some real misfortune in their health.
When I retired sick leave could be cashed into a health savings account at 50% of face value. I didn't feel at all bad getting some heath issues fixed before I retired (A couple of partial cornea transplant surgeries) that ate up a lot of sick leave balance. Annual leave was another story, it was cashed out at 100% of face value. The year I retired I hit my anniversary date with the maximum carry over, 240 hrs and didn't use any until I retired. I think I cashed out somewhere around $25k worth of annual leave. About the only bonus that you can get in civil service.