Of course, he doesn't need to conserve chakra period. Just suck Chakra off whoever he needs. Like
"Oh shit. Kabuto is being chased around by no names. Lulz. I need a chakra snack though. Rinnegan chakra suck activate."
Even if he could probably get more outta, say, Mei.
Spoiler:
Edit: Speak of the ****ing devil.OH! And Onoki says "I grazed your shoulder." And Madara let him. haermm
The ****? Did Kishi visit this thread or something?
Edit 2:
http://www.mangareader.net/naruto/578
Should link it first lol.