What is the best short-term BYOP plan?

I am a missionary outside the US. I have an iPhone 6. Occasionally I travel to the states for visits or conferences and would like opinions of the best short-term plans.
Two I have used in the past:
BlackWireless: Unlimited Data and Voice minutes
I was very pleased the first time using it for 3 months, but they totally screwed up the second time I tried. I ordered a SIM but it never arrived.
Net10: I had to pay for 30 days when all I needed was 2 weeks. Otherwise the service was good overall.

I'm casting a net to see if there are options I have not found.

Prepaid is typically 30 days at a time...