I was able to take opiates everyday for weeks straight with no noticeable withdrawal until one day it just sort of happened. Since then i got on IV heroin for several years and kicked it, then after recovering i noticed that using as little as twice a day for two days straight would cause a mild withdrawal. I finally got clean for about a year and started dabbling in kratom, about 5 times a year at first but slowly, over the course of 3 years i ended up taking it for a couple weeks straight on a few occasions and just recently detoxed from that again.
So for me personally, as far as i'm concerned i can't really mess with them on consecutive days whatsoever. Even 2 days in a row of kratom will give me a feeling of rebound that i would just rather avoid, and using more just slowly makes it worse. It's the most incredibly psychologically fucked up addiction, because i think you mentally become overly aware of the slightest nuances of withdrawal and over time the response time for those recognitions becomes shorter and shorter.
I'm sure the period of drying out will affect this a lot too. So if i stayed clean for 5 years, i'd probably be able to use for a few more days without noticing at first, but it will always creep up again. I try to continuously alter my lifestyle to better accommodate this malady, and overall i think i'm going in the right direction.