This paper proposes a general framework to compare the strength of the dependence in survival models, as time changes, i. e. given remaining lifetimes $X$, to compare the dependence of $X$ given $X>t$, and $X$ given $X>s$, where $s>t$. More precisely, analytical results will be obtained in the case the survival copula of $X$ is either Archimedean or a distorted copula. The case of a frailty based model will also be discussed in details.