A couple of years ago, I worked in the sales department of a distribution company. A customer would call and say, "I need 10 gadgets by end of business tomorrow and I'll pay the shipping." I would then see that the order was overnighted to the customer. Why? Because that was the service the customer had PAID for. Lots of people that use OP's expect the same thing - to get the service for which they've shelled out the dough. That's all.

If a person in pain is eating the cost of overnight shipping, they expect their meds, well...overnight. I think it would make things better if the OP's would be up front about how long it takes to get out an order. A little honesty goes a long way, ya know?

Erin