Board Thread:Ninjago Wiki News/@comment-25095204-20140703085642/@comment-26381381-20150714182236

And time between season is no that long. Just a few days or months, no years ( for example Season 4 and Season 5 - will be Morro waiting one year or longer?). So Ninjas must be of the same age in all seasons (or with a difference of one year).