I use them more and more now with leg workouts otherwise i get knee pain - think is all good as others have mentioned as prevantive tool but i dunno about recovery time being delayed etc

I only wear one whenever the tendinitis in my right elbow starts acting up. I know I can lift without it, but I feel that it keeps my elbow more stabilized, preventing mistakes in my form that could worsen the condition.

Now if you’re a guy constantly testing your strength, I would think they can be considered wise preventive maintenance. Although, I’ve never been wise enough to consider precautions until it’s too late. At my age it’s all about preventing anything from getting worse, LOL

Are there studies that show they weaken cartilage and tendons? Do you mean standard sleeves or the crazy tight wraps people use powerlifting?

I use still use elbow sleeves when I go above 80lbs dumbbells on seated ohp, they consistently reduce the amount of elbow tendonitis pain. I don’t use them on bench though.
When squatting I wear some cheap knee sleeves but I don’t lift more than 365lbs anymore, but they are not near as tight as wraps.

For preventative measures only IMO.
I wouldn't use them with lighter weight. If you can do 6 reps without them, you don't need them. If you're running in the 3 rep range, I would consider them to help avoid strain on the joints.
You shouldn't rely on them and if you're injured, you should focus on injury recovery exercises.

It’s a catch 22. Will it help your lift while still putting proper stress where you need it? Sure. Will it keep you safe in some circumstances? Sure. You don’t have to wear them in your top sets, which is mostly what I’ll do. For example… squats I’ll go up to about 315 and once I feel lubricated, I’ll throw them on for a little rebound and warmth going 400 plus. Think about how the body operates here… I’ll stick with squats. I wear 7mm sleeves and outside of general compression, most assistance occurs once I hit about 10 degrees above parallel. Your quads are firing like crazy once you get past the rebound. Outside of pressing movements, they are kind of pointless imo. Like press said, it can get crazy with some of these wraps/sleeves. It will help with the lift at a certain moment in time, but if used properly… they are money and you’ll grow the muscles without creating too much stress on very crucial ligaments/tendons.

I can see the need for them during squats as they greatly aid bad knees and really help to keep the joint warm, but when I see guys wearing triple ply elbow sleeves for their benching sets then its just another way of cheating and helping the lift. It's well documented they add another 5 to 10% onto the lift adding strength to the triceps, but they will use the excuse of it helps with bicep inflammation Lol

I wear them on my knees for squats only. Presses and Curl/Extension machines I take them off. I beginning to think it's more of a mental placebo, for me anyway. I will say though after 20 years active duty infantry I have shit for a meniscus. I've researched it alot and there are a million "Research" and "Theory" articles. It's like diets. You can find a study conclusion that best suits the answer you really want. Frustrating.