Note: This was written quickly and posted immediately, and quite possibly contains idiotic mistakes. If so, you have my humblest apologies.
Rodney was not addicted to coffee. Sure, he drank it everyday, but that didn't mean he was addicted to it. It just meant that he had a lot of work to do so he had to stay awake, because really, you can't work while sleeping, you idiots. And a cup of coffee can only contain so much caffeine, so of course he had to drink more than one cup.
Yes, Rodney was aware that there were other ways to stay awake, like stimulants. He's not a moron, though; he knows that there is no way Carson will give him them. The only way that would happen is if there happens to be another one of their monthly death-impending situations in which he's responsible for saving everyone's life and absolutely, positively needs to meet an impossible deadline in a day. Even then, though, Elizabeth had to order Carson to comply with giving Rodney the stimulants.
Rodney is not addicted to coffee. He only hoards it to make sure that he can save the city from the everyday stupidity of the people inhabiting the city other than himself - and, alright, Zelenka as well. It's not as though he can depend on the other scientists to fix anything. Rodney fixes most of the problems that pop up in Atlantis while researching new information on the city and the Wraith, and he has to go offworld.
He's not addicted to coffee; he just has too much to do, so he'd really appreciate it if everyone would stop accusing him of hogging it all and glaring at him. How else is he supposed to save the city if he's sleeping because he's much too overstressed and tired? He's only drinking it to ensure he can save their lives. Is coffee really too much to ask for in return?
He is not addicted to coffee.