These temps stay rock steady for an hour or so but then drop off slowly. I'm still not totally sure why but I think the problem is airflow. Every time the temp drops off I open the vents all the way, stick the the ash tool inside the bottom vent, and then tap the bottom grate so that any accumulated ash falls through. Once the fire stoked back up (you can tell from the smoke coming out of the daisy wheel) I close the vents back down and wait for the temp to stabilize.
Do any of the egg owners out there have this problem?
Haha...I read about people recommending that. Never did it.
What you described is what happens when the lump or charcoal is near the end for me. If I have a full load I generally do not get temp swings. Unless it is real windy.
Try briquettes, uniform heat is the best asset of the briquette, and I like Stubb's for flavor you can taste the hardwood, I have even smoked salmon on coals alone and it is bangin.
Lump, no matter the air control, can still be finicky because it is not uniform.