I think you might be.
I'm reading my talk board posts from sillyages ago right now.
( Hoohah Bibbly-bobbly-bubbly-snibbly wib-wib floppit., Wed 14 Dec 2005, 16:54, archived)

You are right.
I am dense. I need to go to the pub.

My First Post : www.b3ta.com/talk/387148
( The Teviot Moose major 5th., Wed 14 Dec 2005, 16:58, archived)

and mine
www.b3ta.com/talk/734072

and while we're at it 1st post on /board
www.b3ta.com/board/4729021
( Boondocks, YEAH! has a massive penis. Everyone is scared., Wed 14 Dec 2005, 17:03, archived)

How disappointing
www.b3ta.com/talk/379826
( Shoosh up your lips Not state-funded, Wed 14 Dec 2005, 17:15, archived)

Awww. I miss monster munch.

( Dr. Shambolic je suis charlie, Wed 14 Dec 2005, 17:05, archived)

And whaddya know
It ended up as a thread about jizz. Nice.

Edit: I'm being dense - how did you find that?
Edit again: All the fucking class www.b3ta.com/talk/31890
( Dekazer, Wed 14 Dec 2005, 17:05, archived)

Follow the links in your profile and then leap back to however many posts you have posted.
Mine is very confusing ... www.b3ta.com/board/1660825
( Dr. Shambolic je suis charlie, Wed 14 Dec 2005, 17:11, archived)

Ooooh
you're an enigma.
( Dekazer, Wed 14 Dec 2005, 17:12, archived)

In case you hadn't worked it out...
take your total number of posts, subtract 1
then in the url it takes you to on the search, change the startfrom number to that..

So for you it should be www.b3ta.com/users/searchposts.php?id=21744&board=talk&start=15301

although that doesn't seem to work for me...
( The Teviot Moose major 5th., Wed 14 Dec 2005, 17:11, archived)

yeah, seems you can't look at other's posts past a week

( Boondocks, YEAH! has a massive penis. Everyone is scared., Wed 14 Dec 2005, 17:17, archived)

Damn, there goes that idea for blackmail...

( The Teviot Moose major 5th., Wed 14 Dec 2005, 17:19, archived)