Matt, the standard request I get is for a roof certification which is essentially what you said. They want somebody to put in writing that the roof is going to last "X" number of years. The requests are even more priceless when you have already inspected the property and notated in your
inspection report that the roof has issues and needs repairs. "So you want me to state in writing that the roof will last at least 2 more years AFTER I've already inspected it and said it needs repairs??????"
Sometimes when you quiz the person requesting the info as to what it is they want to know specifically, they can't even tell you because they don't know themselves. Not that I would plan on doing what they are asking but curiosity drives me to find out what it is they want.