Depends on who your buying from also.
I use priority for almost anything east of the Mississippi. Longer than that, I suggest express, mainly because it comes with tracking, which priority does not offer. I always use delivery confirmation.
In five years of going exclusive with the USPS, I have lost I think 2 queens. (One dead and one lost package) My local UPS store refuses to mail.
All my queens are pulled within 24 hours of shipping. Most are pulled the morning they are mailed. I've gotten queens from others that have been banked and they die very quickly and I always have a few dead. So I think much of mailing success is dictated on the business practices also.
Priority normally is a two day delievery within a couple states of me. Sometimes it has taken a third day. That is also why we do not ship on Thurday, Friday, or Saturday. I try to mail all of them on Monday or Tuesday. This ensures they will not be sitting in a postal center over the weekend. I graft and schedule my queen pulls on a calendar based on shipping orders.
Much of USPS problems or success is also determined how close you are to a main postal terminal hub. I mail from Lewisberry anytime before 4 pm, and they will be trucked to Harrisburg at 4. They then will leave by plane from Harrisburg at 7pm to the next postal hub. Then out from there by truck, or another flight, etc. If I pull in the morning, mail in the afternoon, then they leave that night's flight, they are normally at the customers nearest postal hub within 24 hours.
I have had some problems with isolated places, like Alachua County Virginia. Twice, mailings took a week to get delivered. And twice all my bees arrived safe, alive, and were reported to be doing great. Why it takes that long I have no clue.
Hope this helps.