I counted it.

Err. I didn't count it.

It might be interesting to break up the question into "how long have you actively participated in the community" and "how long have you been reading the site".

I counted it, coz I'm mostly just a lurker here anyway. Far too busy!

I half-counted it. I counted from the time when I finally created an account at lesswrong.com.

I counted it.

I don't remember that far back, so I used my earliest comment (imported from Overcoming Bias) as the date.