I don't know about other states, but here in Washington you can apply for multiple sections at the same time.  Significantly, the administrative fee for applying to take one section is $90, but for each additional section on the same NTS is only $14 (although there is also the $200 or so fee per section that doesn't depend on how many sections you sign up for).  In deciding whether or not to schedule two sections on the same NTS, I have to weigh the administration fee discount against fee forfeiture if I don't get them both done in the 6-month window.  I'm currently studying FAR (the first section I'll take) and haven't decided what to take second.

Has anyone selected multiple sections on the same NTS?