Do I really need to reapply sunscreen?

I didn't used to apply sunscreen regularly, but since last year, I have been consistently applying it every morning. I apply it meticulously because I feel that UV protection is the best habit to start with for preventing skin aging. However, I've heard that you should reapply sunscreen every 2 to 3 hours because it can wear off due to sweat or sebum. They say that some of it might rub off and you need to reapply it to maintain the protection, but it feels like a hassle, and it's a bit difficult to do that on a daily basis. Is it really true that sunscreen needs to be reapplied to maintain its effectiveness?