Reliability optimization in the nano-era needs to account for multiple reliability concerns. Redundant Multithreading (RMT) has emerged as a promising technique to mitigate soft-errors in multi-cores. Since variation- and aging-unawareness during RMT may increase aging of slow cores due to high utilization or lead to unbalanced aging under varying workload scenarios, we propose to leverage variations in vulnerability and duty cycle by means of multiple compiled versions. We perform variation-aware task mapping to proactively reduce the aging of slower cores and thereby maintaining the minimum processing capabilities. Afterwards, we perform an aging-aware activation/deactivation of RMT considering tasks' variable resilience properties and select appropriate reliable versions for the mapped tasks. Experimental results demonstrate that compared to state-of-the-art aging-unaware RMT techniques, our ageOpt-RMT provides improved and balanced aging profiles by 2x on average.