I have not, because typically when I ask questions like this of agents they either don't know, or I get different answers. You guys, on the other hand, are much more likely to have actually done this. This could make Comfort fares very useful if you wanted to book trips where you have a fairly high chance of cancellation, but are fine with keeping the credit for future travel and don't want to pay for a full Lat fare for the flexibility. This assumes you would know this > 60 days out, but still - quite useful. Even if it's last minute the Comfort change fees are very reasonable.