That will vary from state to state. Here, in North Carolina, I believe the statue of limitations for negligence is 3 years.
I would recommend keeping all of your clients’ records permanently, if possible. There have been a few occasions where someone has returned to train with me after 4-5 years and were very delighted to see that I had their old records!
I am with Frank. I keep them for years afterwards and also had instances when clients returned.