The JAA Requirement is for the rating to be revalidated in the last 12 months preceeding expiry however; when the ANO was rewritten in 2000 a mistake appeared where the 3 month requirement for the LPC was mixed up with the 12 month requirement for revalidation by experience. That error resulted in the 3 month window appearing in Schedule 8 and has never been corrected; it subsequently appeared in LASORS. As there is no date of signing on most of the Cs of R then most examiners have followed the 12 month JAA requirement. I don't think anyone is going to get excited about it.
If an examiner charges for a signature go elsewhere!