It's been years since I did this research and can't find my listing of sources.

After a quick deep dive on the topic, I found this: http://www.ncbi.nlm.nih.gov/pubmed/18852035 In short, cells from oral tissues experienced relatively more DNA damage. In absolute terms, it's not much, but reason enough to default to patches, versus oral routes, IMO.

Also, oral nicotine causes all kinds of gingival recession. This is pretty widely known (halfway decent source for this: http://www.ncbi.nlm.nih.gov/pubmed/2388141).

Despite oft printed warnings to the otherwise, you can just cut up the patches to customize the dose.

Duration of release? I believe you should leave it on 24/7. IIRC, it's not that nicotine improves sleep quality, but rather that nicotine withdrawal impairs sleep quality rather profoundly, and as such keeping the patch on at night allows for better sleep. I could be wrong here, though. Been a while since I've researched this.