Conditions:
1) ZERO extrusion. Given my history with an annihilated thrust bearing, I figured it was my problem.
2) After removed the hopper, warming the struder, and kicking the motor on to watch the remains loading pellets feeding, I saw no movement other than rotation and rejection.

Here's what I found:
1) Thrust bearing was fine. I added a couple drops of 3 in 1 oil to both washers and the bearing. The washers were indeed fused to the nylon and shat coupler. I gently removed them and added a drip of oil.
2) I replaced the nozzle, melt filter, and coupler entirely since the original nozzle/coupler was fused together....possibly from plastic creeping into the threads.
3) While inspecting the thrust bearing, I decided to try to reverse the rotation of the auger by had until the remnants came out.

I did find a significant ABS plug which rotated with the auger, but it slid out fine at 190c until reaching the hopper opening. This is when I used needle nose pliers to gently but firmly remove semi-fused pellets and the molten plug.
I reassembled and now find extrusion to be perfect after removing the plug which could not have been removed while the nozzle was off. This took about 45min to figure out and clear.

Hope this helps someone.

I'll look around at various controls and see if I can't duplicate  the functionality of a soak-timer on an an inexpensive single-chip/board...   There are several ways to approach it,  trick will be keeping the cost down. 

As for the heater situation when I get mine I'm adding a second zone just because.      This is one of the reasons I'm going with this brand/design -- it is far more hackable than some of the neatly packaged solutions I'm seeing.    Some of them are rather slick but I need something I can alter to fit my particular madness.

The trouble with a full barrel heater is that the hopper is made of plastic. Again - one could be made out of metal but that creates two problems:

1.) More expensive
2.) Much harder to DIY (some folks create angled hoppers, some mixing hoppers, some accept a soda bottle, etc)

The big boys do water cooled screws too, which is crazy talk unfortunately at this price point.

If you have more ideas, please do share! I definitely appreciate the input, my experience with industrial extrusion doesn't go much beyond reading textbooks and journal articles. A lot of things industrial extruders do would be improvements in the DIY space, but offer poor value in terms of what they improve vs. their cost.

Anyway,  my background is in plastic processing.    Extruders are the core component in extrusion lines and injection-molding machines.

Most modern machines have a soak-timer to prevent you from starting them too soon.    You have to wait a period of time for the cold-slug at the end of the screw to fully melt.   This can take awhile.

What most companies do... we purge our machines empty at the end of a production run.    This gets all the previous resin and colorant out of the system which is vital.   Some resins do NOT play nice when mixed.

Second purge compounds are typically lower-melting point than production resins.   That means a quicker startup if I have to kill the barrel heats for some reason.

Might I suggest hard-coding a soak-timer function into the next generation controller?   And also look at your heater setup.   Most extruders have heating jackets/heater coils the entire length... as well as a provision to remove heat -- like a fan or a liquid cooler.

I understand the goal is to "keep it simple" but there are a few details from the big machines that make things that much easier in the long run. 

After about 2500 hours on my most-used Filastruder (v1.3 with v1.5 gear motor - the one I tore down when extrusion slowed at ~1300 hours), extrusion stopped again - a few mm/min.

I pulled out the melt filter nozzle, and it was clogged nearly completely. This is not unexpected, I was running some trash MG94 that had cardboard and other bits mixed in. I cleaned the nozzle and reinstalled, but no dice - same problem.

I was looking over the machine, and noticed there was basically no load on the thrust bearing. This told me that there was a plug of plastic stuck to the auger that wasn't grabbing the walls of the barrel. I stuck a flathead screwdriver in behind the thrust bearing and slid the auger forward as far as it would go (towards the nozzle) with the motor running. After about 30 seconds, the plastic seemed to grab and the motor load increased, as well as the auger slid back compressing the thrust bearing again. After this, output became the normal ~15 inches/min again.

I think in this case the clogged screen stalled the output, and the plastic stopped gripping the inner surface of the barrel. After that nothing helped short of sliding the auger forward. Interesting indeed, if it happens again I'll be sure to post more here.

I had misunderstood what you were saying about the torch.  Sorry.

Solution is to either clean the existing barrel, or get a replacement. They're cheap enough you probably won't want to bother with cleaning it out.

So, are you saying that my solution is a new barrel?

Using a torch won't clean off whatever residue is causing the polymer to slip on the inside of the barrel, you'd need a solvent that is suited to dissolving whatever residue that was (I would guess Asaclean in this case).

I have used ASACLEAN to clean it between colors.

To my knowledge I did not have any issues with assembly.  It seemed to work from the beginning.

When I clear it out, I take the barrel and auger off and use a torch to heat up the barrel so I can unscrew the auger from the plug.  Sometimes that works, sometimes the plug comes out with the auger.  I just keep warming it up and using pliers to pull the plug off or unscrew it if I can.  Then I reassemble it.

Have you ever had any mishaps along the way? Improper assembly, etc?

What's the total history of polymers and colorants you've run?

After how many hours did you experience the first plug?

What is your procedure for "clearing it out"?