How often do you reapply sunscreen?

I saw in the last beauty tip post that it is recommended to reapply every 3 to 4 hours.

Realistically, reapplying it every 3 to 4 hours wasn't easy either.

If I applied it in the morning, I used to reapply it at lunchtime, but I still reapply it in the summer.

I used to pay attention to it, but now that it's getting cooler, I find myself forgetting about it.

I wish a sunscreen would come out that just requires one application and lasts a long time.