When does beer expire?

Of all the things in my refrigerator, the items that sit the longest are bottles of beer. They are usually left-overs from party where either I bought them for guests or some well-meaning soul brought them over to share but ended up drinking all my wine or more expensive stuff instead. Since there is a good beer pub a couple of blocks down the street (The Herkimer) I never see the reason to drink beer at home, thus it sits in a bin in my fridge - aging.

Dinner tonight was a Seattle Sutton Healthy Eating pre-made dinner of Turkey Meatloaf (coated in "ketchup") with mashed potatoes, creamed corn and purple cabbage. After salting the cabbage and putting some ancho chile powder on the creamed corn, I thought a beer would be appropriate.

I pulled out a Leinie's Amber Light - the neck label touted "2002 - celebrating 40 years"! Shocked that I've probably moved that bottle of beer 3 times and have had it for over 4 years, I took a sip - tasted wet laundry and poured it out. I opted instead for a bottle of apple cider that was part of a christmas gift from my boyfriend's stepfather - probably in 2002. Since I don't drink cider much, I couldn't tell if the age affected the flavor. It was pretty tasteless though, I have to admit.

I've got one last mystery beer left - a big threatening bottle of brew called "The Red McGregor". I'm saving that one for an appropriate lazy night at home. After that, I've gotta upgrade my home brew menu. Blue Moon anyone?