You can liken getting your forklift certification to your driver licence renewal process – that is you must periodically be reevaluated and relicenced. Your forklift training certification will expire exactly three years from the date of your most recent evaluation – or in the case of you having or being involved in an accident, at the time of the accident.
Once your forklift licence expires either through the passage of time or via accident – it is up to you to be re-certified and updated on the records of your employer. Failure to do so could result in compliance breaches if inspected by the OSHA, or potentially loss of your job if your employer requires you to maintain your OSHA forklift training requirements.