I posted a thread a while ago on the topic of;

"Why James Potter left the invisibility cloak in Dumbledore's possesion before he died, even though Dumbledore doesn't need a cloak to become invisible."

My Possible Answer;

James Potter knew that he would die at the hands of Voldemort, but did not know whether Lily and Harry would. Knowing that the invisibility cloak would be stolen afterwards, he left it with Dumbledore, and possibly old him to give to Harry Someday. Thus giving an answer to why Dumbldore had with no need of using it.

Don;t take my word for it though. i get stuff wrong HEAPS!