Heather, I think I know the answer to this, but want to be crystal clear.  My coworker says you can make too much money such that you don’t even qualify for the Public Service Loan Forgiveness Program at all.  My understanding is that the impact of income is that you eventually just don’t qualify for IBR lower payments, your payments switch to the 10 year plan, and that your payments under the 10 year plan still count towards PSLF.  In other words, you don’t make too much money to be DISQUALIFIED from PSLF.  You just lose the advantage of lower monthly payments and the amount eventually forgiven will be lower.  So if I work for the government and make $50,000 this year and somehow miraculously make $500,000 next year and every year after while in the same job, I still qualify for PSLF and the only impact is that what eventually gets forgiven is tiny because of my new income.  Is my understanding correct?  Thank you in advance for your help.

Yep.  You are exactly right.