Naked mole rats are social animals that live in colonies. There are differences of course, but I do not think the evidence suggests that aging is a 'requirement' for complexity. The simplest explanation is that aging is an evolutionary adaption that gives species that age an advantage. Human cells obviously possess the potential to persist past their programmed deaths - that's what cancer is. So I think it's obvious there are no biological limits to us stopping our physical age at whatever stage we want - but I'm equally sure that would involve changes to the experience of being human we may not like (perhaps being in the body of a 20 year old means being in the mind of a 20 year old, for instance).