To be honest, ethical guidelines are so strict (at least here in EU and the UK) that it’s extremely difficult to get any approval for traumatic experiments
Those that do get approval only get it for a very small number of the animals with no room for slip-ups
But to answer your question, it depends on the type of experiment done on them. Lab rats are specifically bred and usually don’t last for many years (most age related studies I’ve seen have had at most 2-2.5 year old mice/rats). Keeping them alive is also costly in maintenance (no disease spreading, keeping them fed, healthy and active etc). So, unless those animals can be used in other experiments, often times experiments end with culling the mice/rats usually via chloroform and saving samples of tissues in cold storage for future reference
Edit: disclaimer, my work is with molecular biology and data analysis, so the mileage in psychology may vary
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