Q. How frequently do you have problems with mail delivery?
A. Only on the days that I expect vapemail.
Q. Am I the only one having this problem?
A. No
Q. Is there anything I could do to improve the odds of successful delivery of my orders?
A. Yes, talk to the USPS hub manager and (have detailed examples of all past issues prepared) and express your lack of satisfaction with delivery times/ failed deliveries/ mis-deliveries of Priority Paid Delivery Service. (It is not acceptable that the problem remains routine unless they have a different carrier on the rout every week.
Q. Is there anything I could do to get my vendors to offer alternative delivery options such UPS and FedEx that are much, much, much more reliable?
A. Ask them if they are willing, there is certainly nothing you can do to make them though.
Q. Or, am I doomed to this problem for eternity, or at least until the local post office branch hires some competent personnel who can read, write and comprehend at an elementary school level?
A. Only if you remain a squeakless wheel. You can tell 100 people what your issue is, but if you don't address it with the party that is responsible for it and is able to address it, you won't get anywhere. If you do not receive satifactory mitigation of the problem, talk to the next person up their chain of command.
Be a squeaky wheel to the person who is responsible for maintaining a squeakless operation.