I have been type 1 for 35 years and have always been told that insulin can be kept out of a fridge (unless the weather temperature is extreme) for one month then discarded. I now use an insulin pump, always have a spare vial of insulin in my bag as well as my insulin pen in case of pump failure and discard the pen after one month even if it is has not been used. My vial only lasts 9 days so it is not an issue. The rest of my stock of insulin remains in the fridge until needed.
That's the advice I got too. Being as forgetful as I am I like to write on the pen in sharpie when I opened it, or put the date it was opened into a countdown app on my phone to see how long it's been opened (one of the holiday countdown apps people use)