Also, SEP revalidation by experience can be done anywhere during the second 12 months, provided the experience requrements are met. New 12 month perio d will run from the expiry date of the current rating.
I signed an instructor off once on her 3rd day in the second 12 months, since she had done 12 hours and had just done an IR renewal with me, thus meeting all the requirement for a SEP renewal by experience.