system
Given the following post, respond as if you're commenting on Reddit:
human
How much time will it take for the CMBR to cool to radiowave frequencies? Won't this have an effect on free electron spins?

If free electron spin is affected by radiowaves, then won't they be affected by what is at some point a cosmic radiowave background radiation?
gpt
There isn't really that sharp of a line microwaves and radio waves - the EM spectrum is a continuum. 

CMB peaks at 160 GHz, RF generally speaking extends from 300 GHz down to a few kHz. In this sense, the CMB is already 'radio waves.'

But maybe if you want to call anything above 3 GHz a microwave, then you'll have to cool the universe by another factor of 50ish. 

Let's make a really rough estimate for how long this takes, assuming a constant expansion rate. It took 13 billion years for the universe to expand to its current size, so it will take another 13 billion to double in size, thus cutting the CMB temperature and (frequency) in half. As an approximate rule of the of thumb, this means that every time you double the age you cut the frequency in half. 

Since 2^5.5 ~ 50, then we will need to wait about 5.5 times the current age of the universe for the CMB to shift down by a factor of 50. That's an ~70 billion year wait. Don't hold your breath.