How long do withdrawal symptoms since one quits caffine usually going to last?

I was pretty addicted to caffine since college and used to go kill the hangover and euphoric outer body feeling when tired and hungover. Now I still drink alcohol ocassinally with friends but for my new years resolution I quit soda, coffee, tea, and all caffine sources and only drink water. At first I was tired all day now I hit a wall at three where i can't keep my eyes open. And sleep through class. When should I expect my body to adapt to no caffine or sugary drinks on a daily basis? It's been a month since i quit.
How long do withdrawal symptoms since one quits caffine usually going to last?
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