Clutch occasionally makes sounds

Sometimes when I'm off-roading or wheelying, basically treating my clutch a bit rough, it'll make a squeaky/whiny noise. It only happens just before the clutch is fully engaged, and only under heavy load. I'm not 100 percent sure, but it might've started after I last changed oil and oil filter.
The oil I use is 10/40 fully synthetic Yamalube. I last changed it a few weeks ago, and I used 1 liter of brand new oil, and 0,4 liters of the oil of an opened bottle that I bought around February. The shape of the bottles were different, but the oil was the same, as far as I know.
The bike has got about 14,000 km on it. That's about 8700 miles.

So, is there any cause for concern? Is it time to change the clutch plates, perhaps?

I wouldnt worry about it, I've heard lots of bikes do it when you abuse the clutch.

If it bugs you changing the clutch disk will stop it for a while.

Nah, it doesn't bother me as long as it's not a serious problem. Thanks, buddy.