When I upgraded my extruder the new assembly came with a little part that made a big change, PTFE (teflon) thermal barrier tube liners, a small tube that the plastic feed through before hitting the hot end. In theory these tubes served two purposes. First, they prevented the plastic from sticking as it went through the feed assembly, resulting in fewer jams. Second, they decreased the area that the filament is being heated to being right at the nozzle, insulating the rest of the filament. But, as always the reality is a little different.
First of all, the PTFE tubes do not decrease jams. If anything they increase them. If the nozzle gets clogged the filament in the tube just gets hotter and hotter until it practically bonds with the plastic tube. I've seen jams so often I've just kind of gotten used to them. And that's okay because while jams are more frequent they're also easier than ever to replace. Just unscrew the nozzle and replace the tube, no need to remove the fan or even take the extruder off the carriage. Many of the repairs in the past that have required me replacing the nozzle have actually been fixed by changing the liner now, so my nozzles have more life. But the other other side of this is that PTFE tubes have become my new consumable, and while they're cheap it's hard to keep those on hand.
Note to anyone in a similar situation, make sure you get the outer diameter of the tube you buy right. In my case it's 3mm outer diameter. The 4mm stuff will not work at all.
You've got to get the right length of tubing, too. Get it too long and you can't screw in your nozzle. Get it too short and the top of the filament will not be insulated from the thermal block's heat and you'll jam frequently because the wrong part of the filament is heating up when you try to change filament. So it can be troublesome.
The PTFE tube also effects what I can print, and this is less good. Going too hot will melt the tube, so I can't do the nylon or some of the alloy materials while I've got the liner. Which kind of sucks.
But the worst part is that your last length of PTFE tube, jammed with plastic, that you're going to gently heat to try to get the jam out of that you, but you sat on the kitchen counter for a second to wish your wife a good morning, looks to a 10 year old like a piece of junk, like the inside of a dead pen. I just watched my son throw my last PTFE tube into a full and nasty garbage can never to be found again. (I tried. [shudder] I tried.) I've got more on order and they should arrive in a few days, but for lack of a little length of tubing my printer is once again sitting idle in my garage.