Yes you are right but, when you know that your PR right is due within 3 months then, you should book the appointment in 3 months in advance to avoid any further delay.Anyway, from a practical point of view I expect that the waiting times to get an appointment for the premium applications will creep up to the 2-3 month timescale anyway (which is the time it takes, on average, to process the applications now anyway!),
Thats exactly what I am saying...With the only exception being EEA3&4 applications who could book in advance of their 5-year time limit approaching to apply for PR.
I dont think UKBA would offer free of charge premium service however, at least it would help to protect your employment or emergency trevelling