Generally, if your cooking time runs longer than the one I use (and mine do too sometimes), it means either the temperature climbed ttoo muchhrough cooking, usually because the cast-iron pan wasn't preheated sufficiently before putting in the oil; or the chicken pieces were smaller than the ones I typically fry. My maternal ancestors were arch-eyeballers, and when the chicken was done, they could tell by looking at it. THey could also tell when the oil was too hot because the chicken was browning too fast, and when the oil had cooled because the sizzle didn't sound right. 
I can do that okay-ish, too, but I'm a lot more okay with my temperature probe (which comes, I believe, from a Mac tool supplier and is meant for monitoring exhaust system temperatures).
Never cooked on gas, so I don't know if there's temperature creep through the process, but in the summer, when it's too hot to fire the woodstove, I get perfectly acceptable results using an electric cooktop. I just set the know halfway between 3 and 4, let the iron pan heat for 10 minutes before putting in the oil, heat the oil to 325 for five minutes or so, and then go right at it. I might have to adjust temps based on how the chicken looks over the first segment; the thermometer doesn't do much good in this phase, because the chicken influences temp swings too much. Cooking on wood is remarkably easier, if you've been at it a while. I know that a typical chicken-frying wants four sticks of oak or five sticks of ash, about the size of my forearm, and if the sizzle is sounding a little anemic I might have to slide the pan over onto the firebox for a minute or two before moving it back to the front lid.
(Note that, typically, the smaller pieces and breasts are done first. Necks, then legs, then breasts, then backs, then thighs. Because I'm old and lazy, I often just fry thighs--everything's done at once.)
Of course, there are way easier ways to fry chicken, but then the original poster asked for a Chef's input. I'm not a chef, but my son is (or was, he finds it more entertaining these days to make craft beer), and this fried chicken recipe is his favorite by several orders of educated-palate magnitude. Of course he was raised on it. And that, more than anything, influences what chicken eaters perceive as being The Proper Fried Chicken.