Well, of course Sith don't want to die. But their obsession with life is also in the context of a Sith Order in which if you're not killed by an enemy, then you're killed by your own master or apprentice. For instance, Filoni talks about a Sith that dies as being a failure, but I don't know of any Sith (even when we broaden things to the EU) that live to a ripe old age and die of natural causes. However, Plagueis seemed to obsessively search for the secret to unnaturally prolonging life, and he failed. Sidious doesn't seem to be following the same obsession, so it's unlikely that he's going to discover anything that Plagueis did not. And it probably won't just fall into his lap. They're only truth from "a certain point of view." The Jedi masters probably were suppressing some teachings, but more because they're dangerous teachings, not because they were greedily hording power from Anakin. And as for the bodies Plagueis experimented on, like that of his master, they were bodies of individuals he killed and then tried to bring back. They weren't the people he cared about, caring about others isn't really a Sith trait. His interest in saving Padme from the beginning was completely fake, so if Palpatine had no intention of saving Padme from the start, why assume the story to be true? Sure, elements of it are, like that there was a Sith Lord named Plagueis who was interested in cheating death, but he wasn't some nice selfless guy, he had killed his own master. He didn't teach Palpatine everything he knew apparently. Also, Sidious' plan goes from I to we we you. E.G. "I have the power to save the one you love" .... "if WE work together, I'm sure we can discover the secret" .... "Only then will YOU be strong enough with the Dark Side to save Padme."