Well it all depends on the type of stuff on the movie (if it's just grandma sitting round patting the dog or if its full of action like kids running around at top pace amongst the trees) and the number of frames (ie the time) of your video.
As I said, most cams record at absurdly high bitrates for home movies (maybe 6-7000 kpbs constant). You can generally get 2.5 to 3 hours into a DVD5, no problems (subject to it being regular stuff like grandma and puppies). Especially if you re-encode (as opposed to transcode), the quality loss might not be very noticeable at all.
You should try it on one or 2 vids and make a decision then.
Either way, good luck.
Regards