If they sandwich the yeast pack, they should go 3 - 4 days with no problem, I guess it depends on where it was kept during transit also . However, 7 days is quite a bit , so if no packs were present, then.....
Jag, you're good people and I'm certainly not taking a shot at you! I thought the following remarks would be useful to illustrate the reality of what an icepack/insulated mailer goes through.
Frankly, I don't put much faith in icepacks. Often the yeast arrives sitting on top of the grain, under the packslip. So the thermal mass and buffering that I wrote about above often doesn't really matter.
A great example of this happened late this past Saturday morning, I drove from my home in SE DC to Annapolis Homebrew (38miles per Apple Maps) to get some liquid Whitbread for some summer UK/Australian brewing.
I keep an insulated mailer and its icepacks in my freezer for runs out to Annapolis HB or myLHBS in Seven Corners, VA (both outstanding LHBSs--I'm lucky to have them!). It was in the 90's and sunny when I made the 76 mile, ~2hr round trip.
I drive a Miata and I'm militant about keeping the top down whenever possible. It was a hot, sweaty drive but waaaay more comfortable than the conditions you'd experience in a 52' trailer during state-to-state transit, a loading dock, or even a delivery truck out for final delivery. I can't emphasize this enough, it is
murderously hot in a trailer.
On the run out to Annapolis I stashed the mailer and its icepacks under the passenger seat. When I left the shop they were anything but frozen, but still quite cold to the touch. When I arrived home it was certainly cooler than ambient, but the yeast was nowhere near where you want to be storing yeast. Fortunately, yeast are tougher than we give them credit for. That said, I sure wouldn't have wanted to drive a further hour.
It's also worth mentioning that the conditions that I experienced were ideal. Your order gets pulled, packed, and then placed on loading dock to await the next truck. During that time, it's getting warmer. Then it's driven to a distribution center, where it waits hours to be loaded into a trailer...all the while getting warmer and warmer.
See what I'm getting at?
With all that said, I still click the double icepack/insulated mailer boxes. Frankly, I know I'm pissing away money, but every little helps.