I bought a sleeve in 2019. It recently has really stretched out and keeps falling down.

Washing and drying the sleeve may help restore some elasticity.

It sounds like your sleeve may have reached the end of its lifespan due to stretching out over time. With consistent use, especially during active periods, it's common for compression sleeves to lose elasticity and effectiveness after a couple of years. While this might not be the case for everyone, it's a normal occurrence.

It's probably time to purchase a new sleeve. However, if you haven't already tried it, washing the sleeve may help restore some elasticity. Washing can remove oils and debris that might be contributing to the stretching. If the stretching is severe or the sleeve doesn't regain its shape after washing, it's likely best to invest in a new one for optimal support and comfort.