As a general rule, as an inspector, I would normally expect to see some level of periodic reassessment, in this case, around every 2 years or so.
This will need to be based on risk and is dependent somewhat on the systems you have to control collections and detect failures. Less control or low failure detection = more frequent assessment.
I would be interested in understanding the documented rationale for extended periods without competency assessment during inspection.
Ask yourself, how detectable and how serious could a failure be?
Do you review this as part of self-inspection, and how often?
What about those trained and assessed, not distributing components for an extensive period, say >3 months and thus becoming unfamiliar with the process. Is their initial competency assessment still valid after such a period, and if so why?
What measures do you have in place to control those collecting components? If you have a fully automated system which disables individuals access cards after a period of inactivity (say 3 months), the risk is probably reduced, but what about manual systems where such functionality is not available?
There is no hard and fast answer to the above, and it depends on the risks, which will be different at each site.