The Sith adhere to the Rule of Two: one master and one apprentice. The apprentice is taught that once they surpass their master, they must take his (her?) place by killing them. In this way, the Sith order increases in power through a Darwinian-like process of attrition.
This means that the Sith cultivate an extreme (if somewhat twisted) form of altruism. The master willingly sacrifices his own life by training an apprentice who will ultimately kill them. All for the greater good (evil?) of the Sith order.
To willingly submit himself to such a harsh requirement, there must be some goal that the Sith master values higher than their own life. It can't simply be the desire for power or domination. If you were that sort of person you would want to enjoy your power, ruling the galaxy etc. You wouldn't train an apprentice who would take it all from you at the first opportunity.
So the Sith must have some higher goal than that. What is the goal that they are devoted to? And was Palpatine on his way towards fulfilling that? If Palpatine were successful in becoming immortal then there would be no more Sith after him. The Rule of Two would cease to operate: nobody could kill him, hence there could be no future Sith Lord more powerful than him.
Does this mean that Palpatine expected the Sith order to culminate in his own person, or was he opting out?
(Yes I know this is really two questions but I believe they are related).