The following list comes from my own experiences, along with bits and bobs I've found elsewhere. I thought the rest of you reenactors might also get a laugh out of it, and/or have things to add.
So feel free to post additions, I'll add them to the list.
(Any period, though try and keep additions "period-neutral" if you can)You know you're a reenactor when...
-Nobody will watch a war movie with you.
-You've worn wool when the temperature tops 100 degrees, repeatedly.
-You won't hesitate to spend $150 on a good pair of reenacting shoes, but $29.95 "dress" shoes are outrageously over-priced.
-Your Christmas/birthday wish-list reads like a quartermaster's supply list.
-You've driven by some open land and thought, "What a great place for a battle!"
-You make career decisions based on if it effects your weekends.
-You are wary of others seeing you change at home, but no problems in the parking lot.
-When you come home after an event you are hit with depression.
-Buying a new vehicle, it must fit all of your gear and tentage inside of it or it's a no-go.
-Come home sore, bruised, dehydrated, sunburnt, and covered with ticks and it was a good weekend.
-For a week long reenactment you can fit everything on your back. For a weekend reenactment you need a truck and trailer.
-You replay a certain scene in a documentary or youtube video over and over again to look at the .2 second frame you were in.
-You've made a nest with your wool to lie in when there's a reenacting "dry season". (Or as my dad says, "Feldgrau Fever")
-Your reenacting room/closet has more expensive items in it than any other room of the house.
-You have more shoes and boots for reenacting than modern footwear.
-You earn a good salary, but are always broke.
-You corrected your history teacher back in grade school.
-While out to eat, you've been asked if you were Amish. (Hey, dey be the triple k! Naw, dey ain't the triple k. Dey somethin!)