3 years, no mention of mileage in the VW Workshop manual.
Image credit to golfdave.
Could never find out if my CS had ever been done due to GDPR and VW unable to tell me, so i've armed myself with VCDS and a bottle of fluid.
Once i manage to get myself a half decent laptop for VCDS duties, i'll be doing it myself.
VW Dealers seem not to know anything about this service item until pushed on it from what ive read.