That’s a neat idea!
Elders might take some time to die from old age, even if their bar was full, and maybe regular birthdays have a random delay, too. So it will be needed to keep aging on for more than just the new year hour. I normally activate it early on the last day of Winter, then switch it back off in the evening of 1st day of spring. It allows everyone nearly 48 hours to "react" if their time is up. It's important to save and stay focused to not play on with aging for weeks, though. One year will be added every midnight. Once I forgot to turn aging off I had to go back to my backup.
