I used to make over $60k as a TCD in the middle if the pack seniority wise. It was 85% of top rate and most every day worked was close to 11 hours since we were always made to help other drivers.
You need to factor in if any cover drivers ahead of you are going full-time. If they are you will move up and get more work. The downside is if too many move up drivers below you could qualify and move ahead of you on the list.
I had quite a few drivers below me on the TCD list who could never get their days in to qualify. I took every route offered and never gave anyone the opportunity to pass me on the cover list.