Linguists have found that semicolons, colons, and even commas, are on the wane in everyday usage, and that many speakers no longer understand the use of a semicolon. Non-writers – and you will see this in emails, forum posts, and other written messages – often do not use punctuation at all, but rather let all "sentences" flow into each other, only putting rows of exclamation marks for emphasis.
These are of course extreme forms, but those may be your readers, if you write genre fiction, and knowing that some of your readers may not readily understand the difference between a comma and a semicolon or a full stop and a semicolon might as well make you hesitate to use it.
On the other hand the semicolon is still in heavy use in literary fiction and academic writing, so if you aim for an educated audience, by all means make full use of all the tools that language provides.
An edit to answer Alexandro Chen's question in the comment below:
John Rudolph, literary agent at Dystel & Goderich Literary Management, writes in a blog post on the "Great Semicolon Debate":
Personally, I’ve had a negative opinion of semicolons, and as an editor I would regularly strike them from authors’ manuscripts. My feeling, echoed by every copyeditor I ever worked with, was that in kids’ books they stood out like sore thumbs. Indeed, I loved the comment from the sixth-grade teacher, who wrote that when she sees a semicolon in a kid’s paper, it’s invariably plagiarized. It’s just not a device that feels natural to a kid’s way of viewing the world, and as such, should probably be avoided at all costs.
But now that I’m an agent and working on a lot of adult projects, I’m finding that in certain contexts and genres, semicolons not only make sense but fill a vital role. Certainly in nonfiction, I agree with the author [of a Times article that inspired Rudolph's blog post] that the deft use of a semicolon can suggest a connection that other forms of punctuation—especially my beloved em-dashes—can’t quite pull off.
With YA being somewhere in between MG (no semicolons) and adult (with semicolons), you are in a grey transitional area where I'd say the use of semicolons will depend on the "adultness" of your topics and writing style. In a light and funny summer romance I would maybe avoid them; in a reflective, thought-provoking, difficult book they might be a valuable stylistic instrument.