You don't need always the 32 bit, it all depends how far you are pushing the footage, and remember not all AE effects there work well with 32 bit. Of course if you shoot RAW or do time lapses form RAW (CR2 or DNG) then 8 bit in AE is somewhat bad idea. It depends where you grade, if your images are graded in ACR so that they fit in histogram well, then you should not get any artifacts unless you do some drastic curves / luts or other extreame color grade.
Other big problem in Adobe world is exporting to a codec that supports more than 8 bit (because encoding in highly compressed final format trough AE is BAD idea - slow and unstable). I have tried many and have not yet found one that I would like, Avid DNxHD was a good candidate but adobe has problems phrasing more than 8 bit deep DNxHD tough can create one with no problem. Other I have found are either too CPU consuming or too big or unstable (I'm in PC, so no ProRes for me). therefor unless I must (client wants) I try to keep to 8 bit files. I have found MXF / XDCAM HD 50 being really good, fast, not that big, 422, there for still useable for some more editing, fx, grading. (by the way youtube seams to love it really fast processing). Stability is key for me, because many times I have really tight turnaround time for my edits, and I can't lose time on crushed renders (when each would they take 2-4 hours or more).
