Lump Charcoal burning time...

Did you fill it up all the way to the bottom of the platesetter? How many places did you light the lump?

You will easily get 20+ hours at that temp on a large or xl. BGE lump or otherwise. A controller is advised for low and slows when your target temp is below 250-275. So little air flow is required to maintain that low a temp, the egg can burn straight down or snuff itself out. You don't need to cook below 250-275 on the egg unless you are trying to stretch a cook out for timing reasons. unlike other cookers, the meat will maintain moisture at higher temps. 

What do you mean by "burned up"?  Lump is not like charcoal. If it is burned up, there would be nothing left with very little ash. Also, the question of how much lump did you put in the firebox?  I start by using 1/2 weber chimney red hot, dump it in the middle, then fill the firebox up to at least the fire ring. Then throw in chips/chunks in a ring around the burning lump. (push it down to where the fire is burning). add PL/LU, drip pan and grate. dial it in to a LEAST 250-275. Bottom vent and daisy wheel are barely cracked (typically < 1/2 inch)  
Should have no problems from there. For the first few long cooks, you want to keep an eye on it so you know how it will behave. 

I have had lump burn for 24hrs and used the left-overs to cook steaks at 600 for another 30 minutes.

duly-noted said:

I recently purchased a XLBGE and cooked brisket on Friday night. I filled it up with lump charcoal -BGE brand, added wet hickory chunks and dialed in ~ 200 degrees. This was about midnight. When I went out the next morning @ 8:00 or so, it has dropped to less than 100. I opened up all the vents and got the temperature to rise. At around 10:00, I pulled the briskets off in order to smoke ribs. And to my chagrin, saw that the charcoal had all but burned up! Really? It burns up that quickly? 10 hours @ 200 degrees? No wonder the temperature had dropped so much...

Were the briskets done?  If so, that egg ran hotter than 200 for 10 hours.  That may explain your lump usage. 

I have a small egg which really doesn't hold a lot of lump. Did a half of brisket at 280* for 10 hours and there was still quite a bit of lump left. In the heat of the summer it only takes a little bit of heat to keep the temperatures up. My bottom grate was only open an 1/8th inch. Come winter I'm lucky to get 10 hours.

With an XLBGE and the amount of lump they hold, I would expect a very long burn time.

My XL burns rockwood @ 250 deg at a rate of .4lbs/hour

When I fill to the bottom of my stone when using a Woo2 I can fit 13lbs in my egg.  I can get around 30hrs from one load.

My XL will run a minimum 24 hrs at 275* on a load of lump up to the platesetter. I just dump and go. No stacking or sorting of lump. 

  onedbguru said:

 Lump is not like charcoal.

?????  I hope you meant "Lump is not like briquettes."