Many long-time bloggers are opening focused, niche blogs these days, and some may find that existing content on their first site may be much more relevant for their newer ventures. But if these articles are already receiving traffic on your main site, it certainly brings up a number of possible concerns on the best course of action to pursue.
This certainly happened to us.
On our travel blog, for example, we had many articles about wine tasting around the world (and tangential wine topics as it has always been a hobby of ours). When we started our wine blog, these were a better fit for the story we wanted to tell and we were left with the options of writing a new variant of the articles outright or simply copying them over. The same is true for my blogging advice articles on my travel blog as well. Now that I write here at This Week in Blogging, many of those articles simply make much more sense for them to live here.
Ultimately, the question we're tip-toeing around here is all about branding- specifically whether or not you are more likely to get more clicks on your original domain or on a more niche-specific one (especially in search results). It doesn't take a big leap to understand that my general travel blog called Living the Dream simply doesn't make sense to be home for blogging topics when a site like this one has better branding for it.
I opted to go the route of copying articles over to my new sites outright, and I have to admit I was a bit skeptical about what would happen. I ended up being pleasantly surprised.