I would definitely put an expiration date on it. The person receiving it needs to have a little sense of urgency to redeem it – 6 to 12 mos. is a fair time. However, I would most likely honor it even if it were expired – especially if it was a client of mine who purchased it. If you honor it, you have a chance of picking up a new client. If you don’t, you run the risk of losing one, possibly two.
Quick story: I had a client pay me for 10 sessions up front – did 2 & said he had to postpone his training & would get back to me. We’ll he did – 2 years later. He said he understood if those sessions expired & was willing to pay for a new package. I told him that I would honor the remaining sessions on the previous package & he was very happy and appreciative about that. That was in 1997 & I still train him, his wife & oldest son – not to mention the people he referred to me over the years. A little bit of good will can go a long way.