UPDATE:
My off grid Ring alarm system with a 4g LTE modem is still working great! In 2 days it will have been a month since setting it up, and we have only used about 2gb of data. This is with 2 outdoor cameras, plus a Ring base station and assorted sensors. We have only checked live view maybe 10 times, and instead check the camera recordings mostly only when there is a motion alert. We will be adding 2 more cameras, and will likely start checking live view more often since we have a 6 gb/month plan.
AWESOME solution for off grid security!!