Yes, you have to set your animation start and end first, then match it in render globals. Like Mike said, if you just animate frames 1-48....and set render globals to 2880....you're basically going to get frames 1-48....then lots of copies of that 48th frame.
Btw, If your animation is 2880 frames, don't forget to set your frame padding to 4, also.
"Terminat Bora Diem, Terminal Auctor opus."