Yes, you gain tolerance after a few days and need to up your intake if you want to get the same effect. Which is why some people drink coffee by the pot (though some people aren't all that caffeine sensitive and require that much right from the beginning).
I only drink 2 to 4 cups a day at most, but I also alternate with green tea (or sometimes black) and energy drinks. Often I'll have nothing but green tea for a few days, and I become resensitized to the level of caffeine in coffee. It doesn't take long to gain or lose caffeine tolerance.
I rarely get caffeine withdrawal headaches because I don't do the drink a pot a day, every day thing that real coffee addicts do. I don't like to anyway because the side effects of coffee (acidity causing heartburn, for one thing) and the caffeine level negates the health benefits with that quantity, and you begin to need it more to maintain your normal level of alertness rather than giving you a boost.
But I do drink coffee an average of 4 days a week, still. Not just because I like caffeine but also because I love the flavor and enjoy drinking it.
Short answer: Don't drink coffee all the time if you are using it as a caffeine delivery system.