Heat Creep
A little about the hot end. There are 2 parts to it. The part with the heater that gets hot, gets the nozzle hot, and melts the filament. There is a part on top, usually with fins, that is supposed to stay cool and not melt filament. The hot part is connected to the cool part. Heat flows from hot to less hot. Heat flows out of the hot part to the cool part and then out to the air, keeping the cool part below the temperature to melt the plastic.
You have something to guide the filament. In inexpensive printers the PTFE tube goes all the way down to the nozzle. The PTFE tube is great because it does not transmit heat well. The PTFE tube is horrible because it breaks down, one of the things it breaks down to is a carcinogenic gas, around 250c, a temperature below what some plastics like to be printed at.
An all metal hotend will have a metal tube at the end so the PTFE tube does not go all the way to the nozzle. It is great because it melts at a temperature higher than your printer can reach. It is horrible because it transmits heat well. They do all sorts of things to lesen the horrible part. Make it out of strange metals, make it from multiple metals, and possibly other stuff. It transmits heat worse than some materials, but better than PTFE.
The fins on top have a fan blowing on them. A hot end usually has two fans. One blows on the plastic that just came out of the nozzle, to cool and harden it. The other blows on the fins on top to help keep them cool.
In the slicer you have control of the speed of the first fan. Different circumstances work better with different amounts of cooling. The second fan you have no control of. It is on when the hot end is on.
Creep
One cause of clogging is the top of the hot end getting got enough to melt the filament, having the filament melt, cooling enough to solidify the filament, and having that filament stick.
This can happen for two reasons. One is that there is something wrong with the second fan. Look at it and listen. Does it seem to be running OK and not hitting something. If not, replace it. Even if the fan looks and sounds OK, you might be missing something.
The second is poor design. The connection between the hot part and the fins might transmit too much heat. The fins might be too small to remove the heat fast enough. The fan might blow too little air to cool the fins. Whatever, you have heat creep.
While you are printing things start off OK. As you print the fins get hotter and hotter. At some point they will get hot enough to clog.
I had a fan break and my printer would clog in a few minutes. Replaced the fan and things were fine.
If it’s all working, but poorly designed, it could take hours before you see a problem. Small prints are fine, but every time you try the 25 hour helmet it clogs.
A different hot end might be designed better. A bigger fan on a poorly designed hot end might cover up the problems. Fixing a broken part will make it better.
If you have a problem immediately it is not heat creep. If you have a problem after a few minutes, it is not heat creep, but it could be a broken fan. If you have a problem after hours of printing, look into heat creep. Feel the fins, be careful not to burn yourself, right when the problem occurs. Do they feel a lot hotter than when you started? Take the hot end apart and see if filament melted in the fin area. If it did that’s not good.