How long does it take to lower an alcohol tolerance?

I am the person who relies on alcohol for a social lubricant seeing as I have social anxiety, I will not drink all week, but come friday and saturday, I tie one on with the boys, and sometimes drink a little too much... Now, when I first started drinking 8 years ago, I could feel that great feeling deep into my legs when I downed that first beer, not drunk or anything, as I am a 195lb guy, but it would only take me 6 beers or so before I needed to level off, Now, it seems when I have my first few beers, I dont get that buzzed, and it takes more to reach the "zone" that I have learned is my comfort level, Its not that I feel I require a higher level of intoxication either, just takes more, I never drink during the week, so shouldnt my tolerance stay fairly low?