Maybe you just hike differently to what I assumed.
I do the occasional hike anywhere from 4-8 miles and I usually drink an extra 1-2L for the day - that's how I reckon I'd double my intake for a 12-15 mile hike. I don't piss like a race horse, the hikes are in 95-105 degree weather, and I go at pace. To each their own.
https://www.goarmy.com/soldier-life/fitness-and-nutrition/co...
Military suggests roughly 4 liters for an active person, for an entire day. Even adding another liter for strenuous and in dry climates, that's far less than 8 liters.
If you're awake for around 16 hours, not sure why drinking an average of 500ml of fluids every 2 hours seems excessive to you. Or why drinking 1L of fluids every 2 hours (when your agenda for the day includes doing a 15 mile hike in hot weather) is considered a lot.
If what I've described above would make you go to the bathroom every 30 mins, perhaps see a doctor.
I appreciate the feedback, but perhaps don't tell me what to do.