Answer first: for a lyophilised solid, transit temperature matters far less than people assume, and transit duration matters mainly because of what it does to the cold pack rather than to the peptide.
Reported ranges from Chinese origins to western Europe cluster around nine to fourteen days with tracking, with inland origins adding a domestic leg and coastal ones sometimes beating the range.
Phase-change pack hold times are a function of mass, latent heat and box insulation, and published figures for small parcels are on the order of a day or two.
The caveat is that a warm transit is survivable for a solid and not for a solution, and the difference is not marginal.
Ask for a hold during a heatwave. The better suppliers agree without being pushed.