I am not aware of any legal requirements. I hold on to my record for a very long time because I often found that clients come back at a later point in time, and it is great to refer back to the original notes.
I only throw records out when clients have passed away.
I keep my client records for as long as possible! Find a scanning software, (NEAT is super easy to use). Then scan away, and backup your scans so that you have 2 copies in case of an emergency. That way you can get rid of your paper copies and have scanned digital copies. You never know when you need that record.