Earlier quoted context omitted.
Amazon has ridiculous internal bandwidth. The costly bit is external. The time delay is largely internal buffer time - they need to pull your data out of Glacier (a somewhat slow process) and move it to staging storage. Their staging servers can handle the load, even at peak. GETs are super easy for them, and given that you'll be pulling down a multi-TB file via the Internet, your request will likely span multiple da…
I was referring to the external bandwidth. Even if pulling down a request takes hours, forcing them to start off peak will significantly shift the impact of the incremental demand. I'm guessing that most download requests won't be for your entire archive - someone might have multiple months of rolling backups on Glacier, but it's unlikely they'd ever retrieve more than one set at a time. And in some cases, you might…
That said - the idea is certainly sound. A friend and I had talked about ways to incentivize S3 customers to do their inbound and outbound data transfers off-peak (thereby flattening it). A very small percentage of the customers drive peak, and usually by doing something they could easily time-shift.