I've done this many times and am doing it again today. I racked off the yeast cake 5 days ago, stored it cool with half inch or so of beer on top, then today poured off half to a second sanitized bucket to ferment 10 gals.
So I'll re-use one fermenter without having cleaned/sanitized it. I'm pretty comfortable with this...casual really. It's been a closed chamber so as long as nothing bad is introduced today it should be fine.
I spary the bucket rim before pouring out the slurry, then clean and sanitize it again after and spray the lid.
My limit so far has been usnig a bucket for 3 fermentations before cleaning it. I've done this a handful of times and have had no infections that can be blamed directly on this process. YMMV