The studies linked above are quite conclusive for room temperatures and higher (up to 37C)
Only minor (less than 10%) degradation even after several Months.
The biggest issues are likely to be Cold and Sunlight.
Domestic fridge temperature regulation is not consistent, particularly when travelling in hotels. So Cold could be an issue.
High temperatures in tropics and regions without electricity are the greatest concern for third world but even they cope with insulin distribution.
Manufacturers play safe and give very narrow recommendations that are often unachievable in some regions yet insulin is still used effectively.
I have seen two studies which indicated severe degradation in the USA but these seem likely to be cold store issues during transport.