Celina_Star said:
All day.. damn, isn't that like, tiring at all?
I used to do this every now and again; I can only speak for myself here, but it's not too difficult.
Continuously vary/regulate the stimulation, have a few breaks for meals, take an adventurous approach exploring your porn sources, go with the flow.
Nowadays if I try to fap for too long I get distracted;
One minute I'm reading erotic doujinshi, next minute I find myself on a Wikipedia page for camel spiders.