Rexburg was adding to the demand on rentals in east Idaho. I brought on a research team did a full rental market analysis of Rexburg designed to be used 24ish months ago. There was virtually no vacancy. Worst case was 97% occupancy. 5% of the market was 3 beds. The rest was 1 and 2 beds and a few studio. There is a lot to unpack and elaborate on in what makes the Rexburg market function but to make a long story short, they are so full, many students/workers are commuting from Sugar City, St. Anthony, Rigby, IF, etc. Currently there is very high vacancy especially in "approved housing" because of the reaction to COVID, but that can change quickly on whim depending entirely on policy changes by a single government official or the school officials.
The greater Idaho Falls area is booming with no signs of slowing down that I am aware of. Prices on property have appreciated dramatically year over year. Rents have increased as well. Most all of east Idaho has moved out of what I would determine to be a cash flow market. Development has been very big. In IF and particularly in Ammon, there are large developments still being planned and built and there seems to be an increasing shortage of "low cost" housing. Idaho has the fastest growth rate in the country, and it's not even close (#1 Idaho 2.1%, #2 Nevada 1.7%). Melaleuca and the Idaho National Laboratory, which are two of the largest employers in the region, have recently seen growth and expansion.
Fundamentally, I do not see a way the demand for rentals can decrease which in turn means I would not anticipate an increase in vacancy and rent drop.