Nobody argues the body does need adequate hydration. As for most things ‘one size does not fit all’.
Should we have 8 glasses of water a day? Probably a good idea if you are an active healthy adult or a growing child.
Health condition, diet, activity and how our kidneys work- urine output – factor in. Losing water (ex. sweat, diarrhea) means you need more. Folks with heart failure and kidney disease have to monitor and limit their intake, so yes intake of water is personalized!
Listen to your body it talks to you – you’ve heard me say this often, well here same applies. Thirst ‘signals’ from our body include not urinating in 2-4 hours and dark-colored urine (although many medical conditions can cause this). Yes, whenever you feel thirsty you had better drink fluids.
Be smart, you know you are out for a hike so over hydrate and carry fluids, conditions and weather can changes.
Note: Caffeine, ice tea is not water, sure it helps but carries complicating facts, furthermore caffeine is a diuretic!