[shilala]

I'm with Todd.
If I don't enjoy a smoke, it's history. Sometimes that's a minute in. Sometimes I'll smoke a bit more out of respect for the BOTL that's given it to me, just to give it a fair shake.
Sometimes I'll smoke it down to where I want to eat the nub. Those are the really, really good ones, in my book.
Sometimes they go south on me halfway through. Even if they were fabulous for the first half, when it goes bad, it goes in the alley.
I'm just not going to smoke a cigar I don't enjoy. Like Tom said, life is way too short.

Boiled down, it's simply "when I stop enjoying it".