I did Uni Lit (as mentioned earlier
) alongside VCE Lit, and I found it useful. My VCE Lit teacher started giving me more difficult SACs than the rest of the class, which I know sounds really nerdy but I prefer to be challenged. Much of what I learned at Uni went into my SACs/exam. I also accessed lots of critical analyses of my texts through the library. Uni Lit has probably risen my Lit study score by a good 5 points or so (though we'll see).
I imagine Accounting would be similar? You'd probably get more practise in Accounting which is always helpful, IMO. And I find reading uni textbooks broadens your knowledge of a subject, and makes you see where things fit in a bit better. It's freeing to not be bogged down by the Study Design from an intellectual standpoint, especially if you have genuine interest in a subject.