I too worked the back office accounting, I’ve seen it all as well. Our Inn at been in business for five decades. Starting in the 90s they starting selling gift certificates to our fine dining restaurant which were a very popular item during the holidays, Mother’s Day brunch etc. The original ones didn’t expire, were just written on fancy stationary. I maintained an excel spread sheet that went back about 5 yrs that we kept a running total of sold and redeemed ones. The older ones were written off. I kid you not at least two or three times a month I had guests redeeming gift certificates that were 10 to 20 yrs old. I guess they would be rediscovered in the bottom of drawer. Our Inn changed hands about 10 yrs ago and the restaurant has been spun off twice since then, I have no doubt townfolk continue to try to use the old ones.