What ensoniq says i right, depending on your computer.... if you don't have a pretty stable computer it's better to render frame by frame.
If you indeed have a stable computer and maybe even a multi core processor, this is a very good way. Have multiple cores will also allow your to render multiple parts at the same time.
Open the files you want to render twice (two opened anim8or windows) and let one render the frames 0-50 ie and the second render the frames 51-100. This way you render twice as fast!
I managed to run 5 renders at the same times on my quadcore (5 times faster render
), but it can't use your computer anymore untill it done rendering.