Is there any general rule of thumb for how long I should wait after my natty cycle to run a pH?
not really. natty cycles dont supress your hpta, they just improve your nut's ability to produce more test. were you taking an ai with your nat cycle? and how old are you?
well if you run good ol daa+erase, give it a a break between because the erase binds to aromatase receptors, and you want it to work 100% during pct or on cycle if you run an ai+wet compound. if you do just test boosters, it doesnt really matter
the thing with test boosters is they increase free test, which will aromatise into estrogen, so your test/estro ratio will be around the same. that kind of defeats the purpose a little, thats why people run erase+daa a lot for a natty cycle