Something like this happened to my wife's grandmother when she was in her mid-90's. In that case, Grandma Gina had been left a monthly stipend by a friend who died in the mid-1950's. About 1985, the insurance company administering the trust sent Gina a letter saying that since their actuarial tables said she should be dead by now, they were going to stop paying the stipend until she could prove she was still alive.
Gina eventually had to have the pastor of her church write the insurance company a letter certifying she was still alive. The pastor kept the letter couched in polite language, which was more than I would have been able to do.
Besides demonstrating the venality of insurance companies once again, here's another lesson to be learned from Gina's situation: The monthly stipend was set at $50/month in her friend's will. There was no provision for cost of living adjustments, or setting the payments as a percentage of the trust instead of a specific flat payment. So when Gina finally died about thirty-five years later, the $50 per month had gone from being a significant part of her budget to a pretty small amount compared to monthly costs. And all through those thirty-five years, the principal on the trust continued to grow, reaching about $300,000 by the time Gina died at age 98. Because of how the will had been written, none of that $300,000 went to Gina's estate, and the insurance company got all of it. So if you plan to leave anyone a stipend like that in your own will, make sure there are provisions to adjust the payments, and what should happen to the principal after the recipient passes away.