Refractory in lower chamber of EKO is crumbling

I know this has been discussed more than once but after 4 years of running my EKO 25 my 'U' shaped refractory in the lower chamber is starting to break up, into many pieces.
I tried searching but couldn't find any of the old posts I seem to remember that show how people have layed out the firebricks.

Those of you who have gone the route of replacing the 2 or 3 blocks in the lower chamber with fire bricks how have they been holding up?

ihookem,
Now that I actually read my own signature I see It's been almost 5 years that the boiler has been running. I've noticed cracks in the blocks but yesterday when I cleaned for the first time this winter behind the blocks the front one broken apart 2 baseball size pieces came off/apart on the side.
AHONA is 2-3 hours away from me so not super close. PLUS I'm a little cheap so I'm willing to try the home-made version out of fire bricks.
I cut a slot in a fire brick for the nozzle overlay last year and it's working great, might replace it this summer so I hope this would last as long.

Just interested in seeing how people did the layout of the bricks.

I looked around some more and searched "firebricks" (was spelling it as two words...). I think this is what I remember seeing https://www.hearth.com/talk/attachments/eko-model-25-lower-refractory-pdf.117272/

Has anyone else gone this route.

Fred61,
From what I read I think some people are getting way less than 4 years. I was feeling pretty happy with my almost 5 yrs. I don't clean every day but rather every few days. Since I used a firebrick with slot for a nozzle overlay last year, the volume of ash in the lower chamber has gone way down. Part of my thinking is that the ash acts as a bit of a extreme heat buffer, it takes the brunt of that blow torch instead of the block??? I'm only talking a couple inches or fluff or so.