Upload & Sell: Off
I have made a couple of trips to Africa for extended periods and here is my strategy:
1. take lots of cards so you don't have to delete images just to shoot, cards are pretty cheap these days.
2. I have a Sanho Album which has been replaced with the Hyperdrive, I bought the shell and put a 500 GB drive in it.
Every night after the last game drive I would load the cards into the Album and copy them to the drive while I cleaned the gear, once a card was full it got a red sticker on it, meaning full, do not use. I set up a folder system on the drive so each card had a unique folder for its images. An incremental backup after the first full backup shortened the copy time and saves battery power.
When I got home I essentially had two copies of each file, one on the cards, one on the drive. Murphy never showed his face, probably the belt and suspenders scared him off. But like you, these trips cost a bunch and the opportunity to return may not come your way again and toying with disaster just adds an element of angst to the entire trip you can avoid.