martyb- You might want to check with your HR office and see if this course is really required for your grade and job series. I have a feeling it's not and that, if continuing education is required, it would come through HR, not the guy you work for. He probably has training funds that he wants to burn and feels he is doing something nice for you, even if it's on your own time. It might be worthwhile to call him and have a nice - not antagonistic - conversation with him, no matter how strongly you feel. There may be other employees that would be happy to do this if you turn it down. And, while I know it might not be pleasant for you if you do so, if it's not required, you can turn it down.
You can't be required, as a fed, to take courses on your own time. But, if it's required to keep your grade, rating, or whatever, and your only choice is to do it on your own time, you have a tough decision to make. I would not mention retiring this early. That can bring consequences of it's own. Also, 21 months is a long time and plans change. I know feds with less than a year to go who were forced to go to 3 or 4 months of training as they needed it to stay certified in their positions. Waste of money - yes, but they couldn't keep doing what they did if they didn't complete the training.