The 2-3 days for priority mail delivery is an estimate. You can't take that as gospel. It will get worse with the holidays coming up and from what I understand, parcel post takes weeks to get to it's destination.
It also took me a month to get a pattern from Canada. It goes faster here in the states but when it hits the border, it's horrible, that's what the shop owner in Canada told me.
I also think it's a good idea to keep a list of people that *consistently* do not send packages. I would be embarassed beyond belief if I didn't send one and then joined another swap but people do it. I've even offered to send packages to people that didn't get a package.
Suzanne