Quote Originally Posted by Yukimura
That wouldn't have happened unless Misa was supposed to die there. However the fact that Rem knows Misa's life span (which should be large assuming that the Death Note that died for her probably had quite at least a few lifetimes that he transfered to Misa) but wants the torture to stop implies that Rem cares about her physical and emotional well being, which could come into play later. But el_boss's question raises a good point, as long as it wouldn't affect Misa's proper death Rem could have killed Watari at least for messing with her, instead she came to Light to get her out, very suspicious.
After all, Ryuk came on earth out of boredom.

Maybe Rem and Ryuk are just there to have plenty of fun, by playing with their puppets...