Hi, Welcome to ECF. I'm doubting the aches and pains and insomnia are from vaping. It's far more likely to be detox from smoking. Even if you were only smoking 8 cigs a day, that's still enough to cause some detox sx, in my opinion, and every "body" seems to handle detox a bit differently. I was at about 2.5/3 ppd of cigs a day when I quit, and I had a horrible time. I did do some coughing to start, but honestly, I didn't cough up chunks of much of anything, TBH, although I pretty much had pneumonia for 18 months straight, so maybe I did all my coughing then? I was also inhaling shallowly, as I couldn't do much else, so that may have had something to do with it.
Vaping is good. Vaping is not the same as cigarettes. With that being said, when you get detox out of the way and have found a vaping setup that really suits you, vaping is fantastic. I never thought I'd be saying that vaping gives me anywhere near the satisfaction of cigarettes and I'm not going to lie, I get the odd craving or two, now and then, but it's nothing like what it was. I will say that vaping is better for: health, finances (provided you don't get shinyitis, sometimes even then), smells (you smell better, and you smell better to others) reducing harm, (I have not gotten pneumonia ONCE since starting vaping, and I had a nasty head cold recently that I am SURE would have turned into at least bronchitis or at worst pneumonia) had I continued smoking, it's fun to experiment with flavors, etc., finding a great vape setup and the right nicotine level is key.
Coils will last different amounts of time depending on your coils (often sub0hm drop in coils last longer, but they are more expensive and require more juice flow) while smaller, mouth to lung tanks at resistances of 1.0 or above MAY last less time, but it also depends on wattage, the tank and airflow, as well as gunking factors (high VG, dark or very sweet juices, etc.) those can kill a coil faster. You will know when it's time to change coils, your juice will get this awful taste, I like to describe it as kind of a petroleum oil sludge taste. You will know, once you reach that point, though you might describe it differently, but one thing you won't describe it as is delicious.
Welcome to ECF and glad you joined!
Anna