When someone drinks before bed every single day, they aren’t getting proper, restful sleep on a night by night basis. Someone in Phil’s position should be getting between 4-8 hours of sleep, 4-6 being a better ballpark because he doesn’t do... much of anything really.
Let’s also not forget that heavy drinking for a number of years can cause habituation and lead to alcoholism, the withdrawal of which can kill a man, as well as leading to tons of miscellaneous health problems including (but not limited to); liver disease/failure, kidney disease/failure, mentation changes, mood swings, physical injury due to impaired motor function, digestive issues, vomiting, internal bleeding, seizures, stroke, and death. There is also such a thing as alcohol induced psychosis and alcohol induced dementia, which we are certainly seeing early warning signs from our boy Dark. The fact that he was able to contract gout (even if only his aunt had it, it would be far more likely to be his father or mother if it were hereditary) points to him being a heavy, HEAVY drinker considering his age.