As long as the half-lives are for both Nolva and Clomid, if you start early, you will just get up to steady levels by the time the juice clears the body.
I actually start mine a few days before cycle end to have it at full strength (or close to it) when I become clean.
I stop HCG 7-5 before cycle end and a couple of days later, PCT drugs begin.
This is all with short-acting esters like Prop and Tren A. (NPP should not differ much)
I have honed this to a science trough trial and error. But maybe it only works for me and not anyone else.