As a long-lived race, witches naturally have a different conception of time compared to humans; for witches, not having contact for twenty to thirty years is pretty much like humans not seeing each other for a year or two.
Ordinary witches are already like this, not to mention those almost immortal beings above the Rank of Great Witch; twenty to thirty years might just be the time it takes for them to have a nap. It's said that the older the witch, the more they like to hibernate.
Even if we don't consider those above the Great Witch Rank who can live forever, looking at ordinary witches alone, the age stages of this race are quite fascinating.
Witches still retain some human characteristics, such as taking about sixteen years to grow from an infant to near adulthood, roughly the same as regular humans, and this 1-16 year-old stage is also referred to by the witches as the 'childhood' period.