In a heroic experiment spanning more than 10 years, now published in Nature, investigators transferred memory CD8+ T cells from heterologous prime–boost–boost-immunized mice into recipient mice that themselves also then underwent this vaccination regimen before memory CD8+ T cells were isolated again for serial transfer. The researchers conducted 51 of these immunizations and serial passaging through 17 mice, with each mouse requiring a 60-day rest period between each of the vaccination boosts, all to better understand memory cell longevity and functionality without organismal age and senescence as a factor. With this strategy, CD8+ T cells proved to be functionally durable well beyond the lifespan of the mice (which tend to live up to only around 3 years in laboratory conditions). Despite induced expression of some exhaustion markers and loss of memory T cell stemness markers, these cells still proliferated in response to antigen, were able to control Listeria monocytogenes infection and had an active memory response.