It seems to be a widespread opinion that increasing the length of existing happy lives is better than creating new happy lives and that it may be better even when the total welfare is lower in the outcome with extended lives. The chapter discusses two interesting suggestions that seem to support this idea. The first is critical level utilitarianism (CLU) and the other is view comparativism. The chapter describes the pure case of life extension versus life replacement (...) and then presents some different views about the value of life extension, indicating some of the arguments in favor and against life extension fail. Then, it turns to the implications of critical level utilitarianism and comparativism in regards to life extension versus replacement, the main topic of this chapter. A case is presented to explain that there is a conflict between intuitions regarding life extension and comparativism. (shrink)