The advice to wear kneepads/sleeves was the best advice you ever got. my wrestling coach told me to start wearing knee pads or he would beat my ass like he paid by the hour. And it wasn't about knee strength, tendons or any of the usual things you would think you'd wear pads for, It's because your knee joint gets a lot of percussion and twisting over the course of grappling.
Every time you go for a low freestyle take down your knee clips the floor. Bang. Your need to post out. what so you use? knee, elbow, foot or hand.
And in BJJ It's much more exaggerated because you are always on your knees, even when you are just drilling technique your patella is having to deal with all kinds of force that it has no idea what to do with.
And in addition to that the neoprene sleeves keep your knees warm from the warm up to the end. Without them your ligaments and tendons [low blood flow] will cool off easily once its technique time and your not moving hard and fast.
So whether your knees actively hurt or not you should wear sleeves just to keep them warm and protect them from percussion from the mat. Smashing your patella off the floor is how that shit gets dislocated and then no training or any fun for you.
I also did a little test where I wore my sleeves for 2 months of squatting and then squatted for 2 months without and my squat numbers were the same. The sleeves get you a little elasticity but other than that you either have strong knees or you dont. the presence of sleeves for 8 weeks did not create any dependency in my highly subjective testing.
When i spar against newbs in rotating partner drills I always tell them that if they dont buy knee sleeves for training then I will tap them mercilessly and in embarrassing fashions. But if they do then I am far less a dick. Yes i know im sure ill be a bad parent.