I think that it can vary from person to person, I didnt know nuts shut down anyways? Mine always seem to work just fine cycle or no cycle. But what you mean is when do they get smaller and go up, that all depends on you.
Nuts shutting down would be when youo are not releasing any more sperm. You still come though no problem and the volume is virtually unchanged as sperm accounts for a very small percentage of the total volume of your cum.
Most testosterones shut you down within 4 weeks. Although it is an individual matter.