Routine brush-up sessions every few months help maintain skills—
https://docs.google.com/spreadsheets/d/1IUaLXRSD2sJLaRRNbxXeWtfL2f1p1nbQfi53AfPVLSg/edit?usp=sharing
Routine brush-up sessions every few months help maintain skills—and tend not to cost as much as complete retraining from scratch would over time!