I thought dragons skeletons were permanent? I have killed 12 dragons so far and only, AFAIK, one skeleton has remained, the others have disappeared and one reappeared several (real time) hours later above my head and fell on on me from the sky, the only problem with this is that it is in whiterun and this seems to be the only one that is now not disappearing so there is a massive big dragon skeleton in the middle of the market district in whiterun..... wtf.....
Oh and i'm playing the game on adept, lvl 25 atm and its really hard. I keep getting my ass handed to me. i love it though, oblivion was such a pushover so its good to ahve a challenge once again like morrowind ^^