Life can be like a TV series. Every season consists of 12 episodes, with each episode being one year. So Season One of one's life will be from age 1 to 12, Season Two will be age 13 to 24, Season Three being age 25 to 26 and so on. I initially was thinking of one season having 24 episodes ( and thus 24 years ), but Shin Shion pointed out that it would a) be too long and b) 12 years would nicely cover the various human cycles.
Anyway, I'm into my second season finale now. I'm heading towards closure, cause I truly dislike cliffhangers. This probably stems from watching too much Buffy - every season has resolved storylines. I like that. Not that I seek closure after every 12 years. But at least once every 12 years, I would like to tie up all loose threads. That makes things feel... kosher.