I used to smoke two packs a day sometimes - usually when I was out drinking in which case I was constantly smoking and up late.

I knew a 3 pack a day smoker. He managed it by always having a lit cigarette. But sometimes he'd forget about one in the ashtray and light another one. I saw him a few times forget about the second one in the ashtray and light a third.

It honestly seemed like a compulsive lighting habit, if he didn't have one in his hand he'd light one without thinking about it before looking in the ashtray. You could get a carton (10 packs of 20) for $25 and I made around $8 an hour then.