I love to get genuine fans commenting on my blog postings. So much so, that I have my blog set to notify me whenever someone posts a comment, so that I can immediately go read it and see who it's from. That includes clicking any links provided by the commenter. So if the comment does happen to be from a genuine fan of my blog, I get to find out what cool stuff you're up to.
However, if the link takes me to, say, a commercial website selling prescription meds over the web, or touting some infomercial-worthy health product, or any other content that informs me you were only commenting to get your spammish crap attached to my blog, I immediately mark your comment as spam and 86 it from my blog.
I check my email several times a day, so spam comments stay up for, oh, maybe an hour at most. And it doesn't matter whether the spam comment is attached to a new blog post, or one months or even years old--I find spam, I report it.
So--spam commenters--like the one whose comment I deleted just a few minutes ago: please refrain from wasting your time and mine, and quit trying to sully my blog with your crap. I'm just too fast for ya.