Quick update: For the moment, OH thinks it's not worth the hassle to try and do anything here. However, he has to go to the States later this year for a business trip and could handle the checks in person once there. So now we only need to deal with the 90-day expiration problem. I think he can contact the issuers (say, next month) and ask them to re-issue the checks. The new checks would also be good for 90 days, so therefore still valid during his business trip timeframe.