FH you you are confusing the upgrade requirement with the revalidation requirement. 100 hours instruction and 25 supervised solos is the upgrade requirement to remove the Restriction; it is not time limited. Duchess Driver is perfectly correct regarding the revalidation requirement which also included a 100 hour requirement, but that was amended by JAA Long Term Exemption No 79 adopted by the JAR-FCL Licensing Sectorial Team at its 20th meeting. It has been with us for about 4 years now.
Your original question said:
How can you revalidate the rating then?
By meeting the requirements of JAR-FCL 1.355 as amended by LTE 79.