Here’s the chance to nitpick all the inconsistencies in Sweet Valley Land. I’ll start with the obvious:
The gals have been sixteen for about 15 years, and have seen there share of Christmases, Halloweens, and summer vacations. [In their defense, it's not like the writers were not aware of this, they just needed to keep everyone the same age for the sake of its readers.]
No one ever goes to the bathroom, gets their period, or has gas.
The twins are kidnapped, stalked, held hostage, attacked multiple times and are never tramatized more than one book (until the Jungle Prom Punch Fiasco).