In those books they're in their 70's but are meant to have the bodies analogous to those of people in their 50's today. Someone might not die of old age until they're in their 100's, but age still comes. It would be possible for a TV series to handwave it but it might feel a little bit cheap. I think if they were to do it today, it'd be better to trim down the 30 years to 10 or so and just skip the idea that many of the invading forces had been born on Laconia and had never seen Sol, which works better in the books anyway.