I block all time sinks during working hours with an exception of 2 minutes every 4 hours to quickly check whether the world is ending. My productivity has skyrocketed.
I was using it for a while, but unfortunately my muscle memory has gotten too good at disabling it.
Maybe I should do smaller increments like you do though. I was previously setting a limited amount of time per 24 hours, but maybe a few minutes every 4 hours would be better.
I found the best solution for myself was the delaying page feature, set to 15 seconds. This added enough friction to prevent mindless checking, but still allowed for purposeful checking without training muscle memory to disable it.
I block all time sinks during working hours with an exception of 2 minutes every 4 hours to quickly check whether the world is ending. My productivity has skyrocketed.