I’m kind of a softy on this subject. I do believe in an expiration but I keep it at 99 days of undocumented abandonment (That’s 3 x 31 day months + a week). If it is a discounted package of sessions, I am a bit more ruthless. I only package sessions for a purpose like: Dropping 3 dress sizes in 3 months. So if after the 3 months a client has missed substantial amounts of scheduled time, I offer to charge the per session rate for what we have done and refund the rest, or put it towards more individual sessions.