I don't have any belief I'm the first author to have ever reached this decision point, but it's an interesting point to ponder, so figured I'd share.
How far would you go with your writing?
When I first started out writing, my standards were sure. For those who've read Heroes Die Young, you know that even if things get a little hairy from time to time, the language is clean (other than the slang term for a lady-of-the-evening that one reader took exception to), and (much to several readers' chagrin) the sexual tension remains that way. The biggest "taboo" (if it could even be considered as such) was Aston's drinking (which is and will always remain his vice of choice).
As time has worn on down this road, I've noticed (and it's been pointed out to me) that things have progressed. The language has stayed for the most part clean (in my writing, at least), but the physical aspects have been getting a lot more risque. Again, to several readers' dismay, it hasn't crossed certain thresholds (what I consider the "what could I show my grandmother" litmus test), but it has taken a decidedly different tone.
So, we get to my latest in-work projects, and at least in their pre-published versions, some scenes cross that threshold. Why this happened could be attributed to any number of factors, but the fact remains that it's out there. Is it a matter of hearing so many readers ask for it? Is it my own personal thresholds adjusting? Do I believe it will help boost sales? It really could be any and all of these, or none of the above.
But when it's all said and done, before these works reach publication, I must ask myself: Do I want to cross that threshold?
And sadly, I don't know...