Accepted answer
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.
More usefully, summer lanes are worse than winter lanes for the pack and no different for the solid, which is why the seasonal anxiety is largely misdirected.
Solid-state stability of lyophilised peptides at ambient is well documented in formulation studies, with residual moisture as the dominant variable.
The caveat is that a warm transit is survivable for a solid and not for a solution, and the difference is not marginal.
Lyophilised solids tolerate ambient transit. That is the whole answer for most orders.