The FRTOL had a 10 year validity as defined in the ANO Schedule 7. Renewal requirements were published in LASORS and if the licence had not been used for 10 years the applicant was required to resit the tests. As the licence was reissued free of charge it did little to help anyones pension fund.
As of 2012 the requirements are in CAP804 which state:
3.5 FRTOL Validity
Stand alone UK FRTOL issued before 17 September 2012, had a ten year validity.
When these licences expire, if the holder still requires to hold an FRTOL, they must
complete form SRG 1106 and pay the appropriate fee.
A UK FRTOL issued after 17 September 2012, does not expire, but it is not valid
unless the holder has language proficiency in English at Level 6, or at Level 4 or 5 that
has not expired.
A stand alone FRTOL was one that was not associated with another Flight Crew Licence. As no mention is made of FRTOLs that are associated with a FCL then the above requirement is the only one currently stated.