In practice, even if air temperature is above 18 - 26oC, provided insulin is well insulated eg pen wrapped in a T shirt, and bag not exposed to direct sunlight, nor left in a hot car etc, then it will take a long time for insulin to reach 26oC. Frio wallets need to be exposed to air so they can evapourate to cool. Personally, if I use a device, which I did, for example when leading a 1 month expedition to Costa Rica and 6 weeks in Chile, followed by 1 month in Falklands, followed by 1 month in South Georgia, linked by 2 x 4 day voyages on HMS Endurance, I used a small & cheap stainless steel vacuum flask filled with fridge cooled water to store insulin cartridges between fridges in various locations on military bases etc. This has the big advantage over Frio of offering physical protection against knocks / crushing / vibrations etc, as well as being very cheap - I've seen 0.5litre flasks for as little as £5, but already owned a couple when diagnosed 19 years ago, which I'm still using. I doubt a £15 - £20 Frio pouch would last that long.
While it may not be officially sanctioned to put insulin back in fridge to extend the 28 day period, I've made enquiries with insulin manufacturing companies, who were happy to confirm that it was OK, if it meant peoiple with type 1 diabetes could go to exciting places.