At both ceremonies at the end of ST09 and STiD there were older ladies (officers) present. STO9 centered around cadets going forth to Vulcan while the rest of the fleet with some older personnel where in the Laurentian System (?) - so there wasn't much of mixture of ages. But apart from some scenes in STiD there wasn't that many older people represented. My theory is that aging has slowed or that people are living longer and looking younger - the product of lifestyle and science but I also believe that with some blending of species - example would be Spock who would still outlive the other crew members because of being half Vulcan. I really didn't even see anyone really over what we would consider 40 in the crowd scenes of San Francisco at the end of STiD.